In the near-future Japan, global warming has brought the large city Yokohama underwater, and only the hills remain above the ocean surface. What used to be one of the largest cities in Japan now feels like a small town. Basically, the existence of the island country itself has been threatened. However, there is no feeling of desperation, devastation, nor hopelessness. People are enjoying laid-back lives, and they seem to appreciate each other's company, enjoying the quiet and peaceful time together. This is especially so with Alpha, a carefree young woman who runs a cafe, named Cafe Alpha. She enjoys her life immersing herself in the beautiful nature all around her. There is nothing more precious to her than spending quality time with her kind friends. Oh, the fulfillment and the joy she finds in life... it all indicates her to be a compassionate human being, but she is not quite a human. She is actually a type A7M2 robot. One day, upon hearing a radio forecast warning an approaching typhoon, her old friend who lives close by invites her to the gas station he runs, worried that her old cafe may not withstand the typhoon. Indeed, the passing of typhoon leaves Alpha with her cafe severely damaged. That's when she decides to go on a journey to raise money to rebuild her cafe, and also to see the outside world away from her friends and the comfort of a peaceful life.

The story follows the school life of the three girls, Yuzuko, Yukari, and Yui, who join their high school's Data Processing Club. The odd friendship between the three make for wacky humor in even the most mundane of events.

Iroe Genma is a third-year high school student often referred to as "Elder Sister" despite her short height. This troublemaking teenager is the president of her school's Model Club, which is dedicated to building plastic models of various objects and structures, such as cars, boats, and even robots. Joined by her two underclassmen, the violent Hazuki "Okappa" Okamoto and the rational Makina "Makimaki" Sakamaki, the small group aims to carry out their club duties but are often sidetracked by a myriad of distractions. From battles between club members to lessons on how to confess to your crush, these three schoolgirls get caught up in all sorts of wacky, and downright outrageous situations!

At the time of the ceremony of entry to the college, a young boy named Ushino Hayama finds Sara a girl whom he met ten years ago. From this day, a change has taken place in him, and notices that can now control some water. After having succeeded the swimming championships, he discovers deep sea diving.