In 1995, along with the release of the original Umihara Kawase game, Shouma Yamabuki wrote and illustrated an 8-part manga series which was published in Comic Burger magazine (this is not that). They also created a 40-page comic story that was published in the Scola/Scholar Hyper Technique guide for the game (this is that).

This "gaiden", or sidestory, chapter uses the setting of his manga series, which is pretty distinct from the admittedly story-light game. In this setting, the heroine Umihara Kawase (whose name is spelled differently from the game version, to denote this is an alternate take on the character) has the mysterious power to breathe underwater and uses an electrified lure as a weapon, and must confront the legacy of her oceanographer father along with her friend Kouichi Shioji.