by:アレンの描き方に悩んでいたとき初代担当Y氏がしてくれた最高の助言があります。
その一言でアレンの一生はガッチリ決まりました。“When I had trouble about how to draw Allen, the first person in charge of me, Y-shi, would give me the best advice. With those few words, Allen’s being was firmly decided.”※Yoshida-shi was Hoshino’s first editor. He was strict and rather intimidating according to the assistant comics at the end of early DGM volumes, but he was competent.
(-shi is a very formal honorific)
I think the last part can be less literally translated as “(the foundation of) Allen’s character was solidly built”.