Okay fine, so I don't think he did Sea Prince and the Fire Child. But that's okay, because there is another Sanrio production he has made available, one whose name was thrown about for decades to me as a sort of mythical Holy Grail of Anime Nightmare Fuel: Ringing Bell. The veterans at anime cons would often bring this up when putting their "anime fandom street cred" cards on the table, as getting a hold of copies of this thing was damn near impossible. Maybe you knew a guy who knew a guy who had a fourth generation copy on VHS, only in the days of snail mail fansub distribution, a person might have to offer something of equal rarity to trade for before getting said copy. And so the Fansub Tape Gods thrived: they had the stuff which couldn't be found anywhere else, and you didn't. You were at their mercy.
So it is that finding information online regarding Ringing Bell can be kind of tricky. Running only about 45 minutes long or so, it isn't something people would normally classify as a "movie," but hey, it was the 70s and OAVs hadn't quite existed yet. It's about a cute little lamb named Chirin who loves to frolic and play, and everything seems like the Sanrio we know and love...until the big bad wolf shows up and slaughters his mother. Fed up with his lot in life, Chirin vows to become a wolf himself rather than wait to be killed and be completely powerless to stop it. It's almost a shonen-style "never give up on your dream!" tale, except for the part where you have to abandon your soul and walk the path of Hell. Ogami Itto would be proud.
If you want to learn more about this obscure bit of Sanrio lore, I reviewed it in greater detail on Show # 43 of the Anime World Order podcast. There's also a link to download it via BitTorrent!