Koichi's really had his youthful appearance forever.
Don't you think that type of fashion is a bit too young looking for you?
My Grandmother is in her nineties and she looks younger than some people in their sixties. She says that feeling young and chewing foods a lot are two big secrets to her youth.
A young young thing has youthfulness on their side. Oh to be youthful and young looking again!
The reading is the reading you learned with the kanji. Same goes for the repeater kanji.