Unico ran in Sanrio’s magazine Ririka (Lyrica) from 1976 to 1979. Sanrio compiled all the comic issues into two volumes starting around 1978. Sanrio then republished the two volumes in 1981 and other publishers would end up publishing the volumes under their name (ie; Shogakukan, Kodansha, Scholar, etc). There is also a gradeschooler version that was released around 1983 and is still being published (now by Pikkapika Comics). I’m not sure if they will republish the regular manga any time soon. It would be awesome if they did though!