Responses
Senku was 15 at the start, physically 19 now.
Suika is now chronologically 19 but physically 15 due to spending 3 or so years as stone.
beta
I was checking the wiki page on Suika's age, (which is 19) and apparently! Senku was actual 15 in the first chapter! Now he is 19, please tell me I'm not the only one who thought Senku in chapter 1 was 17.