This is a detailed summary of 7 Seeds vol. 18 by Tamura Yumi. Don’t click through if you don’t want spoilers.
We start off with Arashi surfacing from his dive and realising the boat is gone. He’s sure Ryou would have told everyone he went diving, so he thinks he must have drifted away from the boat rather than them leaving him. He decides to head west to shore, but it’s midday, so he doesn’t know which way is west, so we waits til the sun goes down.
Back on the boat, Semimaru is still passed out and Natsuo is watching over him. Ango comes over to talk to her and she ends up telling him that Summer B is the “loser team” that was added as a backup. That unsurprisingly upsets Ango, since he feels like the fact that ordinary people and even “losers” can manage to survive in this world makes everything he and the others went through meaningless.
Matsuri comes up looking for Arashi and that’s when they realise he’s missing. Semimaru says they should turn back, but Ryou says even if they did, there’s no way they could go back exactly the way they came.
Botan notices a playing card on the deck, a two of clubs. She then goes down below, thinking it doesn’t seem likely that the chair fell against the door on its own because the boat wasn’t rocking that much. She finds an ace of clubs in the sauna and starts to get suspicious of Ango and Ryou. She goes to their room and goes through their things, finding a gun in one of their bags.Then Ango comes in and asks her what she’s doing there. She pretends she thinks it’s just a model gun and asks him if he’s a fan, she then says that she had just come in to check and make sure there were no fire hazards in their stuff. As she’s leaving, he says she better not have stolen anything, and she says of course she didn’t, and then strips off her top and says he can check if he wants. He doesn’t, but he asks her about her necklace, which she says is just an ordinary pendant.
Once she’s left Ango, she remembers a conversation with Takashi back before the apocalypse. She had asked whether they would be given guns or not and he said no, it would be too dangerous for kids with no firearm experience to have guns, but she was allowed to take one if she wanted. He then says that other countries would probably have guns, and he also says that there are some people within Japan who want to hoard weapons to protect the country. He also says that the guides will be given cyanide if they need to kill themselves at some point. She asks if she can see a list of the other team members, but he says no. Back in the present, she wonders why Ryou and Ango have guns, and she clutches her necklace, implying it contains the cyanide.
Meanwhile, Natsu worries that they might never find Arashi, but Semimaru reassures her. Then the fog rolls in.
Thanks to the fog, Arashi can’t see the sun go down, so he still has no idea which direction to swim. He wonders about sharks, and remembers the monster fish they encountered before. He starts to get cold and lonely and he thinks about Semimaru and Natsu, then about Hana.
Hana is briefly shown floating in the water, then it’s back to Arashi. He feels some seaweed that floats up and realises it’s still attatched to the ocean floor. He ties it to himself to keep from drifting. He starts to feel warm and notices he’s surrounded by jellyfish. The two-page spread shows both him and Hana floating in a sea of jellyfish and he thinks that it feels like he’s being held by her.
He wakes up in the morning and the jellyfish are gone. He resolves to stay alive so he can see Hana again, and he uses the seaweed to make a sort of raft, as well as a second one to be a blanket to protect him from the sun. It’s still foggy, but one direction is slightly lighter, so he figures that’s east, and begins to paddle.
After a while, he comes to what he thinks is an island, but once he sets foot on it, he realises it’s floating. He finds a crab and starts to eat it raw, but thinks of Haru telling him not to, so he decides to do whatever it takes to make a fire.
Back to Natsu, who is of course still worried about Arashi. The boat runs into a bunch of thick algae. They also realise the wind has totally died down, and then they notice a bunch of old ships. Ango and Ryou realise this is a ship graveyard and they have to get out now or they might be trapped forever. They decide to use a rowboat to try and tow the boat, but find the algae is too thick and sticks to the rowboat so much they can’t even move.
Meanwhile, Arashi has managed to make a fire and cook some crab. Then he starts chipping off some barnacles thinking they might be edible, and notices that underneath is not rock, but metal. He explores and finds a bunch of windmills, which he realises are on some sort of floating, perhaps movable, platform. He gets nostalgic at the idea of electricity, and when he looks back out to sea, he sees a sail, the sail he made for their boat.
Back on the boat, the others decide to check out the nearest ship, using a ladder to get across. The boards turn out to be totally rotten, but the undersides are covered in shells and crabs, so they decide to cook them. Natsu is glum that she can never seem to do anything on her own the way the others do, and is always waiting for someone to tell her what to do.
Then Hotaru notices the sun coming out. As the fog lifts, they notice a gigantic ship nearby. Seeing the ship, Ryou flashes back to their test and wonders if they’re actually still being tested.
The ship has something painted on it. It’s a buddha on an elephant, which Chimaki says is Samantabhadra. They think it must be one of the Seven Fujis, but Chimaki says why would there be seven directions, there should be four or eight. He says the missing direction is southeast, which just happens to be where this ship is. He also wonders why Botan wasn’t told about it if it’s one of the shelters. He explains that Samantabhadra represents mercy and long life and says that could be meaningful. When Semimaru asks him how he knows so much about Buddhism, he says he doesn’t know about it from a religious point of view, but from an artistic one.
Semimaru wants to go explore the ship. Ango has a bad feeling about it. Semimaru comes up with a way to cross over by using doors. They’ll lay one down, then another, then when they cross over to the second, they’ll pick up the first and put it in front and continue on like that. Ryou is surprised he managed to come up with the idea.
Natsu decides she wants to come with Semimaru, so Ango, still seeing Shigeru in her, decides to come along as well. In the end, everyone decides to go but Chimaki, who stays to guard the ship.
Before they go, Ango and Ryou have a conversation in their room. Ryou tells Ango he’s stupid, but Ango keeps going on about Shigeru dying. Then Ryou asks him about his hand, and Ango says it seems to be healed, but he can’t move or feel two of his fingers at all; the nerves must have been severed.
Ryou talks to Chimaki before they leave. He tells him to lower the sail once they’re gone and when Chimaki asks how, he says to just pull hard on the rope. He then tells Chimaki to be careful while they’re gone, and a third playing card flutters to the deck.
Once they get close to the ship, they see it’s a very strange shape. They manage to climb up the side to the deck, where they find that the ship is in much better shape than the other ships. They also find that there are solar panels, as well as doors in the floor. Hotaru tells Ryou she can see in his palm that he’s hiding a secret, and he should share it when the time feels right.
They split into two groups and go inside. Matsuri and Ryou go one way and the others go the other way. The lights come on automatically when they go inside. Meanwhile, outside, Arashi notices that the windmills have started turning, and he follows the cable towards their ship.
We also briefly flash over to Chimaki, who gets whapped in the head and knocked overboard when he tries to take the sail down. He gets stuck in the algae and can’t move.
Natsu, Ango, Semimaru, Hotaru, and Botan find the ship’s bridge, which Semimaru says looks like a spaceship. Natsu finds a computer screen that says something is in progress. Outside, Matsuri asks Ryou if he hates boats and he says Summer B sure watches people a lot. He also notices the ship is tilting. Back inside, an announcement comes on and says the doors have been locked and everyone should take their positions. Then the ship starts tilting even further until it’s at a 90 degree angle and everyone goes flying. Arashi watches.
When the ship finishes moving, Matsuri and Ryou are clinging to a railing outside. Matsuri fantasises about Ryou telling her to jump off and then putting her on a raft while he drowns, like the Titanic. He says “I’m glad I met you”. Then the fantasy ends and Matsuri says maybe they should jump off, but Ryou says the ship has stabilised. The doors that were on the floor are now right-way up and inside is a stairway, also right-side up. Matsuri says they should go inside and save the others.
Botan, Semimaru, and Hotaru have been separated from Ango and Natsu. Hotaru finds a poster on the wall of the ship; it’s called the Fuji. It’s turned on its end in the picture, which makes Semimaru scream. Botan says it must be one of the Fujis after all.
Hotaru says this is actually how the ship is supposed to be and that she’s seen stuff about ships like this before. It is able to float vertically like a fishing lure bobbing in the water. Botan speculates that that’s how it was able to survive the cataclysm. So although they’re reassured that they’re not sinking, they realise from the map on the wall that they are now way down underwater and so to get out of the ship, they’ll have to somehow make their way upwards.
Out in the hallway, Ango and Natsu have been separated. Ango is clinging to a railing on the wall and having flashbacks to the cave. He is once again getting past and present, Natsu and Shigeru confused. But he is determined to find Natsu and rescue her. As it turns out, Natsu has slid all the way to the bottom of the hallway and is now all alone and has no idea what to do.
Outside, Arashi turns away from the ship and continues to search for their boat. He is able to slide on the algae using his seaweed raft. When he arrives at their boat, he finds Chimaki stuck in the algae and helps him out. Chimaki tells him the others have gone to check out the ship, so Arashi decides to head over there.
Natsu is all alone and freaking out. She thinks about how she can never do anything on her own and remembers how when she was in 6th grade she was part of the broadcast team, but there were enough other people that she never had to do anything. However, one morning she came in and found no one else was there, so she hesitantly tried pushing buttons to do the morning announcement, but it just made a loud screaching noise and someone came in and shouted at her to stop. Back in the present, she cowers on the floor, wishing someone were there for her to follow. She wishes this were a movie and there was a main character she could just tag along with and be okay.
Finally she manages to calm down and talk herself into actually doing something. She opens one of the doors and looks inside, only to see a bunch of skeletons and spiderwebs and stuff. She tries another door and just finds more of the same and starts freaking out again. Then she finds a photo of a kitten someone must have brought along with them. The photo is labelled “Mimi”. She clutches the photo to her and treats it like a real kitten, crying and remembering her own cat, Nuts, whom she had to leave behind. She remembers Ango telling her to notice things herself, and notices that one door looks different from the others. Still clutching the photo, she taps on the door to see if there’s water behind it, and when it’s clear there isn’t, she opens it, scratching her name and an arrow into the wall beside it so Ango can see where she’s gone.
Semimaru, Botan, and Hotaru have also found a bunch of skeletons. They’ve also found guns lying with them, and then find a storeroom full of guns. Semimaru assumes they’re model guns, but Botan remembers what Takashi said to her and says that this ship is a weapons storehouse.
Natsu finds a big room she assumes is a storeroom of some sort. She also finds a computer screen with an ominous countdown to the “last day”. She misreads the countdown as thirteen minutes and starts to panic. She thinks maybe it’s counting down the time until the ship sinks.
She looks around, but can’t see a way up. Then she sees another screen with a map of the ship and information about it and realises that it hasn’t sunk; it’s supposed to be this way. She also realises that the countdown is thirteen hours, not minutes. When she touches the screen, it gives her a map of how to get up to higher levels and she gets out pen and paper and makes notes. She also notices that there are what looks like missiles in the storeroom, but doesn’t think that’s what they could really be. She tells herself to calm down and notice everything around her so she can tell the others.
Semimaru likes the guns, but Botan tells him not to take any. However, she considers taking one herself. Hotaru checks out the surrounding rooms and finds that some have switched directions and some haven’t, and Botan speculates that there wasn’t enough electricity to fully make the switch from horizontal to vertical. Semimaru leaves to go find Natsu, and manages to sneak a gun out without Botan noticing.
Ryou is tapping the walls as they walk and Matsuri asks if he’s checking their strength. He says “that, too” (he’s really trying to send message to Ango) and says that the walls are strong and haven’t rusted. She says it must be because it’s a shelter, so they built it to survive anything. He says old shelters are dangerous and they shouldn’t have come, but she says in this world, there’s not much difference between dangerous and not, and unlike the old world, danger is unavoidable. He tells her she’s surprisingly clever, which makes her happy. Meanwhile, he thinks he almost realised something, but it slipped away.
We briefly flash to Ango, who is now totally confused and imagining himself in the cave searching for Shigeru.
Back to Matsuri and Ryou, Matsuri asks him why he’s scared of boats and he says because his teacher tried to kill him on one. She, of course, does not know anything about his past, so she imagines a little boy getting kidnapped by some sort of pedophile teacher, and is all upset for him and tells him it’s okay, no one’s going to hurt him now, that sort of thing. He realises she’s got the wrong idea, but figures it’s not worth correcting her. They come to a place where the stairs end, but don’t connect to anything. He is able to get over to a nearby door and tells her to jump across to him.
Arashi arrives at the ship and climbs on. Seeing the electricity makes him realise how much he’s gotten used to living without it. He begins to explore the ship.
Natsu comes to where there should be a ladder to get up to a door, but it has stopped halfway between horizontal and vertical and is unusable. She wonders if she could get across by climing up a different ladder and walking across a beam.
Meanwhile, Semimaru’s playing around with his gun, posing and trying to act cool. Then he senses someone or something coming and is on guard with his gun up.
Hotaru leads Botan to a room where there is a computer on. The screen has the same countdown Natsu saw. There is also a folder on the desktop, which they open to find a video. The video plays a pre-recorded message from the captain. He says they’ve run out of fuel and the solar panels aren’t working, so they have nothing to rely on but water power. They are running out of food and there are no fish. People have taken out guns and started killing each other. They’ve lost contact with the other shelters and other countries. There is nothing left to live for, so he is going to blow up the ship and at the same time, send nuclear missiles to Japan to kill any people still left alive so they can die quickly and not suffer.
While Botan and Hotaru are watching this, everyone else (including the confused Ango and paranoid Semimaru, both of whom have guns) is moving towards something, perhaps each other. Ango sees someone he at first thinks is Shigeru, then thinks is Ukai. He raises his gun. There is a panel of Arashi looking surprised. Semimaru also has his gun raised as someone approaches him. He screams. The final panel is Ryou, along with a thought bubble (possibly Semimaru’s, though these last several panels have been deliberately ambiguous) that says “Ryou!?”.