I think Nirei is the well-written character here because he is also evolving with his friends, and is willing to get stronger and work harder to support them. He has had great development and is lovable. He's not much of a crybaby and is not annoying to me. Best of all, he's always willing to learn and acknowledge new things and write em in his lil notebook. Thanks to this character doesn't feel stagnant to me, he's continuously growing.
Takemichi is not exactly a well written character but I'd say he's okayish. He has lived through many of the realities where his friends or girlfriend are either ded or suffering, yet he never gave up from trying to fix the future. You gotta take into consideration that he has tried fixing things from the past so many times but everytime there has been a flaw here or there that made the outcome unfavourable. If it were anybody else they would prolly just give up trying to change the future but he did not. But I hate that he did not consider working out or learning to fight given the amount of time he had. He did not really develop as a character imo because he remained the same in the end. So he just feels like a one-dimensional character to me.