There are a lot of heroes who have a life-changing event that could define the very nature of them as a person. Case in point, what if Tatsumi had the same past, but outright refused to join the Night Raid, or if the experience made him sociopathic? It is surprising how much that can be possible. A simple mistake or a sudden change of events can change anyone. That's how characters can be realistic. I don't know what would happen, so maybe you guys can be decent enough to explain or make scenarios on what exactly will happen to Tatsumi's character as a whole.