
I don’t really get the point of judging people who date guys who are older or younger than themselves, even if it’s a large age gap.
You date people your own age because you have something in common with them. You date people who are older (or younger) because you feel like you don’t have much in common with people your own age.
Cross generational relationships are pretty common in the gay community, and I hate how straight people see it as all daddy fetishes or perverted old men. Being gay already puts us in a small community; our relationship standards don’t have to be the same as straight people’s.

Even in the gay/ bi community it’s commented on because it can be fetishizing. You have older men after the age of 30-35 already being put to pasture called Daddy and sexualized for their sexual experience. And on the other end younger men barely out of their teens being coveted for their youth. Of course this happens in heterosexual couples just as well. Being part of the lgbtq+ doesn’t mean these issues shouldn’t be acknowledged. There are ways of addressing it that make sense to question age differences and ways that are clearly agist and a prejudice. Of course everyone should be with whomever they love. However in this plot you have a 20+ age gap that is directly related to their difference in maturity, current life goals, responsibilities, and most importantly how there’s a need for secrecy as it could ruin a father and his son’s relationship. The uke was lied to but after finding out the age of his UNDERAGE sexual partner continues to engage in a relationship with man who is not only his son’s age but also his son’s closes friend. Knowing this is wrong but allows it to continue. The maturity level of the seme is none existent, being childish enough to lie about his age, betray a friend’s trust and likely boundaries-having not spoken about how he’s pursing his friend’s closeted father. There so many elements to this plot that are problematic even disregarding the age of its two main character. This stuff does happen in real life too, and the drama of how this would implode an already tentative relationship between a father and his son all so he can continue to get dick is so unappealing to me and I’m sure to many people. I’m sure some can enjoy the fantasy or as I personally know with my own group of gay friends have pursued the said fantasy tried their luck and hope they don’t regret it.

I was mostly commenting on prejudices against age gaps, not on the particular circumstance of it in this manga. I guess I can address that later in my comment.... this is going to get long...
You’ve seen an age gap and have already labeled it as ‘an issue that needs to be acknowledged.’ Daddy and youth fetishization exist, sure, but if you see a couple with an age gap irl and immediately become judgmental and assume a problematic dynamic is happening, then you are probably not questioning unequal power dynamics. More likely you’re just prejudiced against non-conventional relationships. It IS a form of heteronormative projection, of trying to assign what makes a ‘correct’ and ‘healthy’ relationship, and monitor the types of relationships that should and shouldn’t exist.
If someone sees a gay interracial couple, and their immediate reaction is, ‘Well, they must only be together because they fetishize their racial difference,’ what’s happening is that person is trying to dismiss the validity of those relationships because of their own assuming prejudice. Do gay men sometimes fetishize race in terrible and problematic ways? Absolutely. Should this be addressed? Again, absolutely. But to use that as a framework for looking at and questioning ALL interracial relationships is just another way of trying to confirm people’s own (racist) biases.
Age and race makes an imperfect comparison, but I felt the similarities of cultural bias were striking enough to point out.
As far as this manga goes, I’m guessing the mangaka is trying to form a question around the age gap: If a kid has a terminal illness, should they be given the opportunity to have adult experiences before they die if that’s what they want? I haven’t read the raws, so I can only speculate, but all of those differences—maturity, life goals, responsibilities—how important are they when the kid has/had cancer? How does potential death/a-close-call with death change the priorities of a relationship? This is probably the question the mangaka is working towards. The premise seems similar to a very sad chapter in Love Mode.
The hard thing about a lot of BL is that the stories are not just erotic fantasy, like you pointed out, they are also fiction. There are stories with premises and questions beneath all the romanticized sex and unhealthily idealized relationships. The manga industry probably wouldn’t have published a lot of these stories if they weren’t half porn, and a lot of the problematics of BL manga come from that intersection of sincere storytelling and blatant pornography. So I usually read BL manga with that mentality.
I’m mature enough to see the lines between what is fantasy (the porno/jack off material), fiction (the story and questions the mangaka has), and reality. These stories aren’t hurting anyone by indulging in their sex fantasies or asking provocative questions. So why dwell on the problematics as if they were reality? I DO
wish mangago had a better tagging/content warning system so people could avoid the content they don’t want to see. It would probably reduce the number of times I’d have to make this dumb spiel.
The whole setup of this plot makes me so uncomfortable.