Why does in some マンガ 本 it says yuki not yuuki?

i really dont no.... ask yuuki

Yūki, Yuki, Yuuki = it doesn't matter,
all romanizations are correct.

Officially published as "Yuki" in Viz media publications and Chuang yi publications. ファン translations usually use "Yuuki".

because it is very confusing with the name Snow
"yuki" and her name is the same... Yuuki または Yuki.... it doesnt matter.... pronounced the same way

i dont know! i called her yuki for ages but when i read the 本 it 発言しました yuuki. sooooooooo i guess it dosent realy matter. あなた just have to decide what あなた like better.

I think it's to differentiate between the kanji for "snow" and the kanji for "gentle princess", as in Yuuki's name. Both are pronounced identically but are written with different characters. In English translations, "snow" is written as Yuki while "gentle princess" is written as Yuuki.