Analysis:MAO Inhibitor on the Cheese

On the 2nd day in SPHIA, a dying rat is found after it apparently ate cheese that contained the MAO inhibitor.

Inubushi frankly admits that she smashed the rat into the table. But she persistently denies tampering with the cheese. Even though Satoru pushes her hard, she denies it's her doing.

Did Inubushi really do it?

Another suspect
If it's not her, there is another suspicious person.

Enomoto.

On the 5th day in Satoru's route, Inubushi steals the MAO inhibitor and the DMT hallucinogen from Enomoto's hidden room in the basement. While there may be some MAO inhibitor stored outside of the basement, it's highly likely Enomoto put the MAO inhibitor on the cheese.

The reason is to use it as a mouse trap. He was probably annoyed by the rat wandering around, so he set up the trap.