[Torajima-shi Kouhouka (Torajimaneko)] The Secret City of Me and Big Sis [Tigoris Translates]

Kakeru and his towering big sister turn an entire metropolis into their private swim-training ground, where practice means kicking apart school buildings while his curvy coach crushes whole blocks beneath her hips in a straining competition swimsuit. When she catches him putting a commuter train to very personal use, the playful teacher demands a turn with it herself, and their giant-sized sibling session escalates into a full-power performance for the tiny crowds fleeing below. A colossal size-difference fantasy where swim lessons, doting sibling devotion, and city-wide destruction all blur into one secret playground.