Koibito Ijou no Koto wo, Kanojo janai Kimi to. @comic

Fuyu is exhausted from the unrelenting criticism and the unreasonable workload from his boss... Until one day, when he runs into Ito, his ex-girlfriend from college. Fuyu is so happy to see Ito that he immediately invites her out for a drink, and they talked about their old days and new lives. Just as he was thinking that this is a nice kind of friendship, they stumble into a one-night stand... (Source: Ura Sunday, translated)