Responses
Ebihara is 25/26 (he became a firefighter at 18 and not long after his girlfriend died and that was 7 years ago), Shin is 2 years older, Shindo is 30. Genki is the only one that we don't know exactly, but he at least 20 since that is the legal drinking age in Japan. Most likely between 20 and 22.
The ages are pretty vague in this manga. I think the MC is around 16? Everyone at the fire station seem pretty okay with their relationship so I can’t see the male lead being ridiculously older than her