Koichi's Penthouse, as the name suggets, was the residence of Koichi Haimawari, located in Naruhata. The rent cost ¥45,000 per month. After the events of the Naruhata Lockdown, Koichi moves out and the building is demolished.
On the exterior, is just an old penthouse that was lazily annexed on the roof of an old, beat-up building. Koichi suspects that the penthouse was unlawfully constructed.
The entry way opens to a traditional genkan where people can leave their shoes before entering the main room of the penthouse. The main room is rectangular and makes use of a typical open floor plan, combining the bedroom, living room, dining room, and kitchen. Opposite the front door is a door that leads to a small laundry room and a unit bath with a bathtub, sink and toilet.
The right side of the main room is covered by hardwood flooring and serves as the kitchen and dining room area. The kitchen counter houses a sink, a dish rack and a stove while cupboards are affixed on the wall above. There is a small refrigerator located near the entrance to the laundry room that Koichi usually stocks up with snacks and drinks for his guests. Atop the refrigerator sits a rice cooker and some condiments.
The left side of the main room has tatami flooring and serves as bedroom and living room. The furniture includes a bed, small table, cushions, dresser, bookshelves and a flat screen television. The dresser is filled with collectible All Might hoodies that Koichi cycles through as his Vigilante costume. After the formation of the Naruhata Vigilantes, there is an extra area separated by curtains, where Kazuho Haneyama can change her clothes.