Yuki continues to work with Natsuki, Haru, Akira and Inoue on the boat. Yuki is having lots of fun fishing. Yuki's grandmother Kate is being released from the hospital. Yuki wants to hold a surprise party and catch a big tuna for her. Inoue warns Yuki never to fish at Akemi (an artificial reef in the sea) because apparently a boat went missing around there years ago. However, the more Yuki and the others try fishing for tuna, the more they want to check out Akemi in the hopes of finding tuna there. There's something really strange about that place.
Yuki and Haru visit Kate at the hospital
Yuki has been working with Inoue and Natsuki on the boat helping customers fish for three weeks now. Yuki is gaining confidence everyday. Not only that Yuki is also having lots of fun fishing. When Yuki and Haru goes to visit Yuki's grandmother (Kate) at the hospital, she comments how tan Yuki has become. Kate tells them she should be able to leave the hospital by the end of the week. Both Yuki and Haru are excited and Haru wants to plan a celebration for Kate returning from the hospital. Yuki says since Kate likes Tuna, Yuki wants to try catching one! Akira continues to keep a close watch on Yuki and Haru, spying on them through hidden cameras. It seems he is part of some sort of secret "Duck" organization.
Akira visits Erika's grandfather, Heihachi who works at a local shrine, to inquire about "Kamikakushi". This is the legend about the dragons that used to whisk away people, and the goddess that seduced the dragons into submission. Heihachi believes in the legend and says he's been having a weird feeling lately. Heihachi leaves Akira with a random joke about catfish.
Akemi, an artificial reef
It's tuna fishing day for Haru, Yuki, Natsuki and Inoue. They suit up with a special belt to support their fishing rods (so the tuna doesn't snatch them away). Yuki is somewhat surprised how hard catching tuna can be. Since tuna are so large and fast, teamwork is necessary between the driver of the boat and the fisher to lessen the tension on the fishing line and rod. Unfortunately they don't catch any tuna that day, but Yuki is still determined enough to practice the luring technique at home. The next day is a work day on the boat helping customers fishing again. They happen to pass by an artificial reef called "Akemi", which is marked by a huge pillar coming out the ocean, it is made to encourage mating between fish species. Akira asks to fish there, but Inoue says no because there is a ban on fishing around Akemi. Natsuki explains quietly to Akira that people don't fish around Akemi because a boat went missing a few years ago in that area.
A tuna takes the bait!
Inoue teaches Akira how to drive a boat. Since Inoue is busy that day, Akira invites Yuki, Haru and Natsuki onto his boat to fish for tuna. After hours of no luck, they finally decide to check out Akemi despite Inoue telling them not to. Yuki was is able to keep his cool and reel in a tuna on his second attempt. Everyone is ecstatic!
Haru is out of control?
Just then, it gets dark all of a sudden and it seems that Akemi has also disappeared. Misaki and Inoue are waiting for Natsuki to come back to the shop. Just then, Heihachi drops by carrying fishing gear and comments how the sea god is in a bad mood since the kids went to fish at Akemi. Back on the boat, they locate Akemi, but it's definitely a lot farther away than it used to be, not to mention the sun is now down and the boat has lost some fuel. Akira concludes that it must be some sort of memory manipulation, that somehow their memories were erased. Then an un-naturally huge bait ball appears near the boat and Haru seems to lose control of himself. Haru starts using his water gun on everyone and fish fly out of the sea! Akira pulls out a gun to defend himself, but it is soon lost.
Yuki and tuna
Meanwhile Inoue and everyone are worried about the boys. Thankfully somehow the ship crashes on a small rock island without anyone getting hurt. Haru, Natuki and Yuki wake up later, Akira used the flairs to signal for help. Once they arrive back on land, everyone is thankful that they are alright, despite how dumb it was of them to fish at Akemi. The next day, Kate's welcome pack party goes off without a hitch. And Yuki is genuinely sad that summer is coming to an end. Haru also seems to be really down on himself.