With this art style choice and being the MC like half the size of the more mature cast, its only natural for him to look very young, though, if this was your intended look for the MC since the very beginning, I'd suggest you stick to it, unless you also aren't genuinely satisfied with it and wish to change it a bit to suit "your" tastes.
I truly hope your are not changing characters up because of other people complaints, cause you will never be able to satisfy everyone.
P.S. I personally like the actual MC look