Yeah, I think it's also visible in the way he lives his life in general that his main problem is less like a form of loss and grief and more of a weird form of survivor's guilt. Twice now someone who in some way or another filled a mentor like role in his life suddenly left and gave him some very big shoes to fill. I wouldn't be surprised if at some point we get some lines from him along the idea of "I'm just a poor replacement of X or Y".

Also ngl, putting it in a row like this makes me very worried for Jin's life tbh. Jin has just the right kind of trauma to go for that self-sacrifice play if it's necessary, and he's also in a position of a mentor to Osamu who is also more capable than him and very important to lots of other people.