Quick answer — Ryuuhei Watanabe worked on Love Live! Superstar!! (Assistance), Love Live! Superstar!! Season 2 (Assistance), Days with My Stepsister (Assistance) and 6 more anime.
Ryuuhei Watanabe worked on Love Live! Superstar!! (Assistance), Love Live! Superstar!! Season 2 (Assistance), Days with My Stepsister (Assistance), Gabriel DropOut (Assistance), Love Live! Nijigasaki High School Idol Club (Assistance), Boogiepop and Others (Assistance), The Misfit of Demon King Academy Ⅱ: History's Strongest Demon King Reincarnates and Goes to School with His Descendants (Assistance), YOHANE THE PARHELION -SUNSHINE in the MIRROR- (Assistance) and 1 more.