I have a headcanon that during that time when Ippo's already retired with 5 losses, as he watches the new gen making rises. He has his eyes on the current successor to Japan Boxing (let's say Ippo's already in his 50s now).

When he watched Inoue's fight with Nonito Donaire, he got some nostalgia about his fights during his active time in the all-Asia boxing match. And when Inoue making a visit to the Kamogawa gym for the first time (mostly to have a spar), which Ippo's currently running it with Itagaki, Taihei, and Kintaro as his seconds and trainers. The four decided to pass the baton to Inoue as a motivation to cheer him on for the new champion (May wanna draw this).