Phew. Don't scare me like that. I guess you're just a little sister. Episode 6

Mei transfers to Hatagaya Academy as Souta's classmate. Souta and the Quest Dorm members go on a trip to the beach and forest. Souta is revealed to have a fear of the ocean due to his traumatic experience after surviving the Premium Ambriel incident. Souta meet Kurumiko, the Cleric, which exhibit the "Story Flag", which show story progression. Kurumiko's parent is revealed to be the victims of Premium Ambriel. While Kurumiko shows Souta her secret place inside a cave, they were trapped by the high tide. Souta saved both of them by breaking Kurumiko's death flag by making Kurumiko his little sister, just like how he make Okiku his older sister. After being saved, they met a mysterious girl in white.