@HauntedPizza @idgi @herpestofderps @yamigosaya @hgbhgbhgb
Being a western, 18 year old is the age when you're a adult who can make their own decisions and have a relationship with another adult of a different age group. People might feel uncomfortable about the age gap but two consenting adults should have the freedom in pursing a relationship regardless of age gap. It's not pedophilia nor is that the case in this manga. The guy in the manga isn't dating a loli or a JK (high school girl).
P.S.
Most Japanese graduate from high school by the time they turn 18, so I doubt the FMC is JK (high school girl). A lot on manga seem to romanticize JK relationships with older adults without addressing things like power dynamics and sexual exploitation that happens very much in Japan (JK prostitution with older males).
The legal adult age for a Japanese is 20 though and according to Japanese law a individual (like the MC) can date a 19 year with parental consent. I assuming the MC does that.
Something really questionable in Japan, in japan the age on consent is 13 years old, the lowest among Asia (the Philippines is 12 years old).