- Real Name: Ogihara Keisuke (荻原恵介)
- Stage Name ILMARI
- Birthday: June 17, 1975
- Blood Type: A
- Birthplace: Helsinki, Finland
- Height: 5.6 feet (171cm)
- Weight: 132.4 pounds (60kg)
- Influences: The Pharcyde, Black Eyed Peas, Microphone Pager
- Favorite Artists: Green Day, Supanova
- Most Memorable Song: Mahiru ni Mita Yume
- Special Skills / Traits: Beatboxing, worst at drinking (can only have 2 glasses).
ILMARI is considered the most handsome member of RIP SLYME due to his European looks as a half. His mother is Finnish while his father Japanese. While English speaking artists who use their secondary language in there works are somewhat of a niche in the Japanese music market, ILMARI does not use any Finnish in his music. The name ILMARI is considered his middle name in Finland, in which he decided to use as his stage name. In the same primary & middle school as RYO-Z, they became the founding members of RIP SLYME. After switching several schools, ILMARI then left for an international school. There he met fellow RIP SLYME member PES, who both shared a distaste for school. Quitting in the middle of his final year, he returned to Tokyo, reunited with RYO-Z to form a unit "Gibinibanko" (ギビニバンコ).
During his school years in Hawaii, he was often called "Ketsuke" (ケツ毛 literally meaning arse hair) - a name which he hated. He has remarked that it lessened his chances with women because of that reason
ILMARI returned to Finland in 2002 along with his group members where they shot photos and footage for their shortcuts! DVD & their photobook RIP STYLE. They as well held several concerts in Helsinki, and one in Rovaniemi.
ILMARI's special skill, beatboxing is featured in several concerts and along with friend Kei in the song "By the Way" in their TOKYO CLASSIC album. He owns a dog (Tibetan Spaniel) by the name of "Ban" which was featured in the special solo concerts.
On May, 2010, he married the model Ebihara Yuri.
ILMARI with two members of Dragon Ash (BOTS & Furuya Kenji) & SHIGEO of Skebo King created the short lived group Steady&Co in 2001. Their aim was to create a much lighter folk influenced form of Hip-Hop against emerging genres such as J-Urban.