First Love Again

Masahiko Sakaki is the head of a furniture import company, happy to be in the casual relationship he's in. He wasn't supposed to fall for his business client, Kazuki Okada... A heartbreaking love story between two very pure adults. Includes a bonus story about what happens after!
(Source: Renta!)
Note: Sakaki also appears as a minor character in Signal, a story set two years prior to the events in "After a Storm".

Two years have passed, and Sakaki and Okada haven’t been getting along well as of late. Okada is determined to make things work, but the younger man remains dissatisfied. Where exactly did it all go wrong?