Revolutionary Girl Utena: After the Revolution
a.k.a. Shoujo Kakumei Utena
By Chiho Saito
Viz Media
I don't actually know if this is a sequel to the manga or the anime
Revolutionary Girl Utena (boxset)
a.k.a. Shoujo Kakumei Utena
By Chiho Saito
Viz Media
Distinct from the anime. Both were written by Kunihiko Ikuhara, but the manga was subject to more editorial meddling.