Shall I Swear True Love, Makoto? Please Be My First

Twelve years ago, Makoto-bobo, Airi's surrogate older brother, moved to Tokyo to become a chef. Airi chases him to his bachelor pad in Tokyo, to make good on their childhood promise. So, why does Makoto-bobo still treat Airi like a kid after all this time...? Now's the time for Airi to show him she's a grown woman, so he'll make her his bride!!