Asanuma's a supernatural enthusiast and member of his school's Sci-Fi Club—the kind of guy who reports UFO sightings and generally keeps tabs on weird stuff. He shows up in the Black Moon arc as an underclassman who really looked up to Mamoru, but his big moment comes when he witnesses something he can't explain: Mamoru healing himself and then getting zapped by Makoto. Convinced he's stumbled onto proof that the Senshi are aliens, he corners Makoto about it. She denies everything at first, but once Asanuma mentions hearing Luna talk to Usagi, Makoto caves—confesses the whole thing and even kisses him on the forehead for his trouble. He pops up briefly again during the Infinity arc, and later in the Stars arc when Usagi needs Mamoru's American phone number and figures he might know it.
The anime barely acknowledges him. He gets a throwaway scene in episode 169 where he shows up at Mamoru's apartment trying to track him down for some PC Network club meeting, rings the doorbell a bunch of times, and eventually gives up. Usagi watches him leave and mutters something about him being suspicious. He's not even named on screen, though his name shows up in the credits.
Content compiled by AnimeList.moe from publicly available sources.
