Osakana wa Ami no Naka is a story based on manga by Nekokichi Ranma about Tsukamoto Yuuji, a young businessman and great swimmer, and Matsui Takahiro, who is still attending school and is also a beginner in swimming.

Second part of .

Young kendo prodigy Ranmaru Samejima captures the attention of Kei Enjoji, the illegitimate son of a yakuza boss. Kei, determined to form a bond with Ranmaru, cultivates a friendship built on trust and sacrifice, which soon turns into love. After saving Kei from a yakuza hit-and-run attack, Ranmaru is forced to give up kendo forever, and the two are left with only their faith in one another. Vowing to support each other far from the world of the yakuza, the two begin living together as a couple. However, when a mysterious figure from the pair's past returns in pursuit of Ranmaru, they are thrust back into the world they fought so hard to leave—and their love may not be strong enough to survive it.

Ever since moving into his own apartment, quiet high school student Kei has been looking for a new thrill. He soon finds himself playing mahjong, but his whole life takes a dramatic turn when he is forced to play the game with a criminal group. Even though the odds seem against him, Kei is able to outmatch the others. Instead of claiming his reward in cash, however, he decides to take an abducted girl named Amina under his wing. Due to Kei's skills and cold playstyle, the mysterious Hideharu Seki takes an interest in him, introducing him to mahjong parlors and new potential opponents. But when matched up against an experienced player named Doujima, Kei is severely outskilled and only narrowly escapes going into serious debt. If he wants to protect his new life with Amina, Kei must find a way to outwit these shady characters and come out on top in every game he plays.