Ruka

Who Is Ruka? Meet BABYMONSTER’s Powerhouse Main Dancer and Rapper

Ruka is a Japanese K-pop idol and a member of the YG Entertainment girl group BABYMONSTER, where she serves as the group’s Main Dancer and Main Rapper. Born Kawai Ruka (河井瑠花) on March 20, 2002, in Yamaguchi Prefecture, Japan, she’s the eldest member of BABYMONSTER and one of the first Japanese idols to debut under YG Entertainment, alongside fellow member Asa. If you’ve ever watched BABYMONSTER perform live, you’ve probably noticed her hip-hop-rooted movement style and sharp rap delivery — those are the two things she built her whole idol identity around.

From Shibu3 Project to YG Trainee: Ruka’s Early Journey

Before she ever set foot in YG Entertainment, Ruka was already performing. She debuted as a founding member of the Japanese idol collective Shibu3 Project in 2017, dancing with the group’s Blue Class for about a year. That early stage experience mattered more than most fans realize: by the time she joined YG in 2018, she already had real performance instincts, not just raw talent.

Once she became a YG trainee, Ruka spent roughly five to six years developing her craft — making her the longest-trained member of BABYMONSTER. Her dance instructor, Leejung Lee, has praised her deep understanding of hip-hop choreography, while YG founder Yang Hyun-suk reportedly said he’s never had to critique her dancing. That’s a rare compliment in an industry built on relentless feedback.

Becoming BABYMONSTER’s Final Member

YG introduced BABYMONSTER’s members one by one throughout early 2023, and Ruka was announced last, on February 6, 2023. She debuted with five other members on the pre-debut single “BATTER UP” in November 2023, then completed the group’s full seven-member lineup on April 1, 2024, with the mini album BABYMONS7ER and its title track “SHEESH.”

Since then, she’s become one of the group’s most recognizable performers, known for a rapping style that BABYMONSTER’s producers describe as naturally “hip-hop,” even when she’s not actively performing. In November 2024, she co-wrote and performed “Woke Up in Tokyo,” a Japanese-language duet with Asa, on the group’s first studio album, DRIP — her first real songwriting credit.

Personality, Style, and What Fans Love About Her

Off stage, Ruka comes across as calm and a little reserved, but fans who follow her closely know she’s got a playful streak — she’s an only child who says she loves drinking milk every morning and has been dancing since she was around six years old, often practicing in her dorm during free time. Her nickname among fans is “Iruka” (a playful nod to the Japanese word for dolphin), and she’s fluent in Japanese, Korean, and English.

She’s also the type of idol who quietly puts in the extra work: she loves Pilates for conditioning, and she’s mentioned wanting more behind-the-scenes footage of BABYMONSTER’s rehearsal process, which says a lot about how much she values the craft behind the performance.

Ruka’s Role Going Forward

As BABYMONSTER continues rolling out new eras — from the Hello Monsters World Tour in 2025 to their third mini album Choom in 2026 — Ruka remains one of the group’s core performance anchors. Whether it’s her rap verses or her choreography leadership, she’s consistently cited by fans and critics alike as one of the group’s most technically gifted members.