For me, Japanese gokkun came later as I was more exposed to American style cum-swallowing videos with people like Kristina Black, Aurora Snow and so on. Actually, how I got into cum-swallowing was quict by accident. Someone older than me (no age talk) caught me jerking off, proceeded to give me my first blowjob, and when tried to pull away as I was about to blow my load just gripped me harder as I filled her mouth. Being the age I was I freaked. She just smiled, opened her mouth, showed me the load inside and swallowed it. Then coyly said "where's the sperm?". That led to quite a few adventures with her always ending with her swallowing. Since then, it's also a bit of a turn on when a lady says sperm, but that's another story.
First Japanese gokkun was a video by Nao. Don't remember the movie, just remember Nao, then Nana (half japanese and half american), Chika Eiro, Nanami Nanase (living off semen video is a classic) up to Nana Ogura. Actually, from her first video, Nana Ogura has been amazing.