Kiss effect: fusion into the vessel for a goddess(that's what I got)
http://www.mangahere.com/manga/kaprekar/v01/c001/30.html
http://www.mangahere.com/manga/kaprekar/v01/c001/31.html
http://www.mangahere.com/manga/kaprekar/v01/c001/32.html
I stumbled upon this, but it seems to be faux yuri, and a guy was introduced in chapter 3 so I'm not particularly happy. However, there is a kiss for each time they transform it seems, and a series with kissing as the prime mechanic is bound to have some way to have some fun with it in different ways(for instance, a evil villainess kisses one and they fuse into a dark goddess, but that would probably be a long way off). Up to 3 chapters translated.