Futa rule 34 porn from The Idolmaster games. This compilation has some of the best pictures. Ill look for comics next.

Idolmaster futa comics:

Idolmaster Futanari Manga by Momo no Suidousui Part 1-8 (probably in the right order)
[Idolmaster] LOVE IN A MIST Futa Manga Yomosaka
[Idolmaster] Omake Hon Futa Manga by Takemura Sesshu
[Idolmaster] Angels stroke 89 Shibu × Ana Futa Manga by Kutani