BOKU GA KOTAERU KIMI NO NAZOTOKI

Not chapter 5. The webmaster missed the upload for conclusion of the second case (where Rinne accuse Ai about the graffiti on her desk) and the beginning of this case.

This is the end of volume 1 novel. Seems like they won adapt volume 2.

In this case, Iroha is asked by a senior to find the truth about a case that happened years ago. At that time, there is another senior boy who was bullied. Based on the explanation back then, the bullies are smoking in the storage room, and the boy is locked there all night to clean it up for them. The client, whose house is right behind the storage, saw him and accompany him all night. In the morning, the boy is found, dehydrated. After the incident, the boy transferred to another school (he is actually smart enough to go to another school), while the leader of the bullies focused on her track club and went to national competition.

After the investigation, Iroha came to a different conclusion. The bullied boy and the leader of the bullies are actually dating in secret. To keep a face, the leader lock him out, but they have planned an escape. Theres a wrench hidden outside, that can be retrieved from hole on the wall. He is supposed to open the window bars, but can do so because the client is watching. Thats why, its actually that girls fault that the boy she loved almost died from dehydration. The bully actually had prepared a way to rescue her boyfriend.

Rinnes sister praised Iroha. She never thought Iroha can make up a better lie than she did to clean up the mess. What actually happened is, the pair is having sex in the storage room. The bully girl never smoke, proven by how she had healthy enough lungs to go on national track competition. What they thought are burnt mark from cigar is actually hair dye. She dyed her hair black (she had lighter hair colour, but strict sport club would want to enforce discipline), and it rubs off when they e having sex. The boy have to stay in the warehouse because they got found out by the client, and if the school knew they had sex, they would be in trouble. He stayed there as distraction while his girlfriend escapes, but at the same time, he couldn escape.

Rinnes sister cleaned up the case as follow. He told the boy, her girlfriend is more worried about getting found out rather than her boyfriends condition. They broke up, the boy move to a better high school, while the girl focus on sport after the heartbreak. Its the perfect ending, because to the teacher, romance will just stop them from realizing their full potential, so she made a story that gives both her version of a better future.