Dazai and Mori had a kind of agreement...

Dazai suffers from insomnia, which most often led to new attempts... Mori made an agreement with Dazai that if Dazai couldn't sleep, then let him come to Mori. Of course, at first Dazai didn’t come to Mori at all, but when Mori realized this, he forced Dazai to write more reports, explaining the reason - Dazai began to come.

Mori’s office is arranged so that he has another private room. When Dazai cames to Mori, and Mori sends Dazai there to sleep. As a last resort, if Mori could get distracted from work or something, then Mori would talk to Dazai.

But the fact that Mori sends Dazai there also means that Mori is up all night, because even though Mori has some degree of trust to Dazai, but sleeping in the same room with a potential killer is a pointless idea and a wasted death. In addition, Mori himself is quite distrustful and cautious.

When Dazai goes to sleep in his [Mori's] room, Mori sends Elis with him, who quietly sits or speaks with Dazai until Dazai fall asleep. After all, Elis is Mori's ability, which Dazai knows, and Elis shares the same memories with Mori. Elis doesn't know more, but she doesn't know less than Mori.

Dazai has been comming Mori for the past few days. Dazai doesn't admit it, but Dazai sleeps better when he comes here.

Just like now, Mori hears a knock on the door.