|Kanji||加賀 優樹 (かが ゆうき)|
|Age||15 - 16|
|Relatives||Haruko Kaga (Mother)|
|Friends||Satsuki Sasahara (Former Crush), Kaoru Nanase (Girlfriend)|
Yuuki Kaga (加賀 優樹 Kaga Yūki) is a character in Tsurezure Children. He is in class 1-6 and the Vice President of the Astronomy Club who later takes up the role as the Astronomy Club President.
Yuuki has grey hair that is parted in the middle and lime-green eyes.
Yuuki attended the same school as Kaoru Nanase ever since they were young.
Kaoru is Yuuki's childhood friend and love interest. Yuuki had always kind of known that Kaoru had a crush on him, and in chapter 193, he confessed to her right before sending a picture of both of them underneath Spica to their Senpai, Satsuki.
Satsuki is Yuuki's Senpai, the president of the astronomy club (which Yuuki is part of) and his former love interest. After Yuuki confessed to Satsuki in Chapter 172 and she rejected him because of her relationship with Hideki Yukawa, he was heartbroken, although he eventually moved on where he started dating Kaoru Nanase.
- The name Yuuki means "excellence, superiority, gentleness" (優) (yū) and "tree" (樹) (ki).
- Yuuki's surname Kaga means "add, increase" (加) (ka) and "congratulations, joy" (賀) (ga).