When Akira announces he was a boy in the first book "Ai wo Utau Yori Ore ni Oborero" so does the fact Akira goes to Dankaisan the boys school next to St. Nobora (Mizuki's school) Things start to get rough when pressure against Mizuki dating a boy from that school rise.
(Source: MU)
Background
Ai Ore!: Danshikou no Hime to Joshikou no Ouji was published in English as Ai Ore! Love Me!'s volumes 4-8 by VIZ Media under the Shojo Beat imprint from May 3, 2011 to May 1, 2012, as well as in eBook format from June 17, 2011 to July 2, 2012.