Mamoru Akasaka

Mamoru Akasaka is a young detective with the Tokyo Metropolitan Police Department and the protagonist of Himatsubushi-hen, one of the arcs adapted into Higurashi no Naku Koro ni Kai. In 1978 he is sent to Hinamizawa to join Kuraudo Ooishi's investigation into the kidnapping of a cabinet minister's grandson, a case at the time linked to a local anti-dam protest movement. Waiting for him at home is his pregnant wife Yukie, soon to give birth to their daughter Miyuki.

He initially comes across as naive and inexperienced, but wins the respect of Ooishi and his colleagues over a game of mahjong that reveals an unexpectedly sharp mind. In Hinamizawa he befriends Rika Furude, who speaks to him in her "Adult Voice" and warns him of tragedies to come, including the deaths of his own wife and of Rika herself. Not understanding what she truly means, he is unable to prevent either.

Years later, in Matsuribayashi-hen, Akasaka returns to Hinamizawa having trained in traditional-style karate to cope with what he lost. Driven by his memory of Rika's warning, he single-handedly defeats a squad of Yamainu led by Tetsuro Okonogi and works alongside Ooishi to persuade key adults, including Jirou Tomitake and Kyousuke Irie, to help stop Miyo Takano's plans. In TIPS material for Tsumihoroboshi-hen, an older Akasaka revisits Hinamizawa in 2005 to look into the Great Hinamizawa Disaster, eventually meeting an adult Rena Ryuuguu.

He is voiced by Daisuke Ono. His surname combines the characters for "red" and "slope," while his given name, Mamoru, is a homonym of the Japanese word for "protect" — a fitting detail for a character who keeps trying to save Rika from her fated end.