I don't know how it is in Japan, but here woman sometime married with man that can go to 20 years older than them. Sure, there's generation gap and many other thing as said in the manga. I kinda understand with the MC here, he has his own priority, that's why he never thought about dating a girl, especially if she is much more younger than him.
It's just not impossible to actually date a girl when she's still in high school and wait 'till you can marry her. Tho the road ahead will be hard for him.