In the 4th episode, they featured an AP for another character O_O... Never have I seen an anime where Age TF is featured for more than 2 characters.
In the 3rd episode, one of the protagonists saved two children from being hit by a truck, and they were discovered to be half bloods of vampire and mermaid. The white-haired girl has more mermaid blood than that of vampire, and the brown-haired is the other way around. The 4th episode was pretty much a fan service, where the protagonist group goes swimming. The white-haired child grows in her school swimming suit right after diving into the pool. The process, however, is quite poorly shown and is hard to notice.
(3:24-3:34)
http://www.animefushigi.com/watch/yo...-uta-episode-4
It seems that the Age TF for the brown-haired girl might be featured in one of the later episodes as well.