Sayonara Color

Shohei works as a doctor in a seaside hospital. One day, a new patient is admitted to the hospital with ovarian cancer. Shohei is surprised to recognize Michiko, his first love from high school. Shohei has been leading a dissolute bachelor life, paying for the company of high school girls and dating an older woman who works in a local bar, but in reality, for the last twenty years, he has not forgotten Michiko. Unfortunately, though, Michiko doesn't remember him at all.
(Source: AsianWiki)
~~ Adapted from the song "Sayonara Color" (サヨナラCOLOR) by SUPER BUTTER DOG (スーパー・バター・ドッグ).