Love Lettters - S1.E20

One day, there was a love letter with "F" and initials in Murai's shoe box.

Actually, it was a girl "Kujirakawa" in 3rd grade and 2nd class who was asked by a friend to give it to Murai. However, the initials of the Whale River are also Fuyumi and "F". I suspect that Kusano and Fujikichi are actually from Kuregawa himself, but in reality it was from Fuyumi's friend Akane Fujita.