Embraced by Gentle Love (2005)

Kotani lives in a shabby apartment and aims to be a scriptwriter. The only view from his north-facing window is the lewd acts of two men engaged in broad daylight in the apartment opposite... One day, a film company asks Kotani to write a story about gay men. He decides to observe the men in the apartment opposite, but when they realize they are being watched, their affair escalates day by day. When the apartment landlord introduces them to the two men, things take an unexpected turn...