Шіодоме Акіра

Akira Shiodome is the son of Akari Sakishima and Itaru Shiodome, and also Miuna Shiodome’s younger half-brother.

He is very mysterious, who only listens to Miuna. He is shown to be very shy and timid. He enjoys playing kancho with Hikari Sakishima and Shun Sayama and after Manaka awakens, the two enjoy playing with each other. He lacked in confidence when he tried to confess to Manaka that he likes her by a note, but after Manaka thanks him, he gains the confidence he needed.

(Source: Nagi no Asu Kara Wiki)