My Boy (2015)

Blurb:
Satoko Tawada first encounters beautiful 12-year-old Mashuu practicing soccer by himself in a park as she’s heading to work. Later that night, he’s still there. Satoko, who had played soccer herself when she was younger, decides to help the kid prepare for his tryouts. When Mashuu doesn’t make the first team, Satoko continues to work with him, encouraging him not to quit and supporting him at the games. Their emotional connection strengthens as the two spend more and more time together, and fill the emptiness in each other’s lives. Mashuu comforts Satoko after her ex-boyfriend betrays her. And when Satoko learns that Mashuu’s parents are largely absent, she starts to become more involved in his personal life. Have Satoko’s intense feelings for her young friend crossed the line from maternal to inappropriate?

Source: www.anisearch.com/manga/30601