Nishina Tesura wa Mitsukaranai

The second volume in the Nishina Tesura series! Shunta Momochi (nicknamed Momotaro) has been slacking off, until he receives a call for help from Tesura, who says she has been kidnapped and imprisoned. She manages to escape at the last moment, but against this backdrop, a series suicides by high school girls jumping off the roof, and a student group called "Ayame" comes to light. A new kind of mystery about a high school girl who calls herself an "old lady" and an ordinary "unreasoning" salaryman!

(Source: Kodansha, translated)