Higher Ex

Once Ryusei's group a.k.a Ballistik Boyz from Exile Tribe wrote a song called "Higher Ex", he realized how much he misses his ex boyfriend.

Or

When Masa has to sing "Higher Ex" he thought that he was making a huge mistake, specially because he was finding hard to expect how much he was missing his ex boyfriend (Ryusei) and wanted to ask him for a second chance.