Dogi's past isn't really that important. He grew up in Felghana, his family died, he had friends, he left. This is Ys, not Kiseki, that's all we're likely to get.
As for his strength, he works out a lot. This is a setting that has winged humanoids, dragons, magic rings and functional alchemy so wall-crushing isn't really something that requires deep explanation.
Yotaka: well, as a fan of Dogi, his past is important to me. ^^
Chester did the same of Dogi(they were partners in training and all), and he is not as strong as Dogi. =/ So, his strenght didn´t come about training and work, only. And real muscular men don´t be able to break walls like Dogi does, believe me.
Well Dogi is a different frame than chester.... he's the type that builds muscle quickly, whereas I'm sure Chester doesn't. And that does exist in real life. Just imagine him as very strong AND well trained.
And no normal body builders can't break through walls, but normal towers don't launch red-headed heroes into the upper atmosphere.
Sorry, I wanted to say normal, not real. Ys is Ys, and reality is reality, of course. I can say a lot of fictional muscular mans, and anyone is able to break walls like Dogi. Chester and Dogi are pupils of the same teacher, so I think he trained them equality, at the same time(if you remember the anime, Dogi knows how to use a sword).
So, that´s what I think maybe there´s something in his past that we doesn´t know.
I'm actually interested in when and where did Adol and Dogi meet again after Felghana. Adol probably headed straight to Xandria, so I guess it was after the events of Ys V when they met again. Dogi was not in Ys V, right? And where did Adol go after Xandria?
Hmm, that's not actually fleshed-out very well. Ys VI says it's 3 years after Ys V, so there's definitely room for adventures meanwhile. I don't think Ys V or Ys VI make any mention of when they reunite.... it's sometime in those years.