The series follow the story of a high school boy who lives in Tokyo, and his childhood friend, Hakatano Donko-chan, who is from Hakata and really talks in Hakata dialect! People around her sometimes get confused because of it, but her dialect makes them smile!

Don't you want to meet with a woman who falls in love, likes to dress up, and arrests felonious offenses? What if she fights for outrageousness of the society with the sounds of the howling siren, and yet, enjoys her love life and friendship? This is how the 21st century-woman with strong will and gentleness would be like. And without doubt, attractive woman are to be surrounded by attractive guys.

大学考试在即的高中三年级生武宫夏辉（深田龙生饰），在经历失恋与学业低迷的双重打击后，被姐姐介绍与她的男友小早川苍太（浮所飞贵饰）一起学习补习。原本对完美温柔的苍太心生反感的夏辉，却逐渐被他的笑容与温柔举动吸引，意外萌生出不该存在的心意——对“姐姐的男友”的禁忌恋情由此展开。在矛盾与自我挣扎中，少年迎来属于夏天的成长与初恋。

Toko Amano worked as a detective, but to take care of her sick husband she quit her job. After her husband passed away, Toko Amano now works as a crisis management expert. 3 days ago, Toko Amano's former mother-in-law rode on an express train with beds. She witnessed a man strangling a woman and told the train conductor, but he thought she imagined it. The police later searched for the woman's body, but could not find her. Toko Amano boards the same express train that her former mother-in-law rode. She looks for the dead body.