Unusually for me, I've stayed engaged/invested in both the game and the character and enjoyed them despite very, very minimal actual writing time and energy. I can see playing Jun again, hopefully when I have more time and brain cells to better unfold him for everyone else to engage with.
Vague general inspiration includes Ancient Detective, a bit of The Imperial Coroner, a little bit of Encyclopedia Brown and probably a tiny smidgen of Miles Vorkosigan, plus all of the most nerdily enthusiastic freshman students in my intro classroom each semester.
So if I could do it over with infinite time (and more importantly, energy) I'd just have him hang out with people a lot more, generally, and give him a chance to react to surprises. Maybe also try to find some ghosts or spirits for him to be completely oblivious about. 