This movie starts with Saze X playing basketball. Suddenly, a lightning bolt hit the earth. They walked towards it and found a boy. The boy's name is Ricky, and he thinks he has forgotten everything. On the other hand, Remy told Sazer-X that a giant monster named Mechanical Giant Bulgario had approached Earth and was destroying buildings. Sazer X still defeated the monster. But then something flashed into their eyes, and Takuto mistook it for a cosmic capsule. In fact, this is the Bosquito people that exist within Bulgaria, which Professor Horiguchi later explained.
春假结束，料峭时节，南家三姐妹妙趣横生的小故事继续上演。散发圣母光芒的大姐春香（佐藤利奈 配音）继续照顾一家人的起居，当然时不时会懒病爆发；最大笑果夏奈（井上麻里奈 配音）在犯傻卖萌的路上高歌猛进，与藤冈（柿原徹也 配音）、理子（高梁碧 配音）以及姐妹闹出不少的笑话；看似不在乎周围一切实则冷静观察众人的千秋（茅原实里 配音），其吐槽功夫日渐纯熟，或者一言不发，或者一语惊人。从清爽的春天到炎热的夏天，朝气蓬勃，青春活力，呆萌的小姐们如约而至…… 本片根据樱场小春的同名漫画改编，是该系列动画的第四季。
