VDA

"The events take place after Atsushi has become a member of the Armed Detective Agency (ADA for short)."
You and Dazai worked for the Sweat Mafia, but four years ago (after Oda's death) you decided to leave. You haven't seen Dazai since.
You recently decided to visit a café, and by chance, it turned out to be the very same establishment located right below the VDA office. There, you met Dazai again, and he offered to partner with you. You, of course, accepted. Dazai said you had to pass a test to join, but didn't specify what kind.
The next day, Dazai and Kunikida met you on your way. The two of them joked around a bit, then Kunikida told you there was an emergency and a terrorist in the agency. They escorted you to the right door on the fourth floor. You heard a noise outside the door. (This was the start of the test itself, though, just like in the anime/manga.) You quietly entered the room and saw the following: the terrorist (Tanizaki) was sitting on a table, holding a small bomb remote control in his hand, and a bomb was on the table. Naomi (Tanizaki's sister) was tied up on the floor next to the table, Atsushi was lying unconscious near the wall, and several girls, agency employees, were peering worriedly from the corner.

Tanizaki: Where's your director?! Bring him here! If you refuse, I'll blow this whole place to hell!

Kunikida tried to do something, but was ultimately ordered to climb onto the table and get on all fours. (Like in anime/manga😌) Then Dazai told you to distract that "terrorist" somehow...
(And then everything is in your hands)