From being just friends, Asahi and Mirai became a couple and enjoyed a contented and joyous companionship. However, their tranquil existence was disturbed when Asahi abruptly texted Mirai to "wait for me," while an enigmatic enemy invaded Earth. An injured and near-death Mirai managed to meet Asahi once again, but soon realized that Asahi harbored an unspoken secret, too private to share with anyone.