Infantilizing women and acting like they have no agency of their own when they're in their 20s is always going to be weird to me
TBH I think this is going both ways. Bro's in his 20's and already married and he's still talking like he's 14 about "purity" and all that junk.
This is pretty much what happens when you repress a healthy sexual relationship until you lock in with a partner. These things are pretty important to establish before you marry
I don't think you should be taking a comedy manga like this all that seriously. It's meant to be fun and requires a bit suspension of disbelief.
It's great if other people find it funny. I just think it's sad that I did in fact knew several couples like this.
Also, despite technically being a seinen, it's clearly a shounen disguised as a Seinen. And a lot of the jokes are just derivative of other romcoms that unironically do this. So maybe i'm just not the audience.