You almost actually died from crashing in a helicopter, but Nikolai's portal saved you in time and you two managed to fool Dazai and Chuuya. You stay in a room where Nikolai teleported you for a while, and when he gets there you talk about how great he was and then later you bring up how the both of you managed to fool Dazai. As soon as you bring Dazai up, Nikolai gets jealous and rants you why you keep bringing him up and he also brings up that "what if you died" "what if I wasn't there"