Ookina Tamanegi no Shita de

Synopsis

In 1985, Bakufu Slump released the song “Under the Big Onion.” The “Big Onion” refers to the gilded ornament on the roof of the Nippon Budokan. The ballad tells the bittersweet story of a first love, with two pen pals planning to meet for the first time at the Budokan.
The film portrays a love story where the characters fall in love with someone they’ve never met in person, communicating only through letters and notes. Kamio plays Takeru, a college senior who has lost hope for the future, while Sakurada portrays Miyu, a nursing student who is single-mindedly pursuing her dreams.

(Source)