I guess being a Taiwanese does make someone able to discuss homosexual marriage casually, which I'm pretty happy with, but also it's very rare in Japanese-made doujins.
(Shika Cka being Taiwanese is just my guess, one I'm quite confident in)
(Another example being Mushihara who is known Taiwanese)
Nationality aside, in the epilogue Iroha's brother Asahi is shown wearing a wedding ring-style ring on his left ring finger and it's known he and Noi are a couple, so it's possible gay marriage is supposed to have been legalized by 2040 in in-universe Japan making it a legitimate topic to bring up in a doujin.