About
Hiroki Kai, known by his nickname "Crazy Karo" (くれいじーかろ), is a Tokyo-based running coach and ultrarunner from Kashiwa, Chiba Prefecture who left corporate work in 2020 to become a full-time "playing coach," training others while continuing to race at an elite level. A prolific racer and YouTuber who documents his training and races for a large domestic following, he built a track and road background (2:17:09 marathon PR) before turning to trail ultras, where his trademark is finishing fast — at the 2025 Western States 100 he sat 22nd at mile 48 before closing into 10th place in 16:22:46. He earned his Western States Golden Ticket with a runner-up finish at the 2025 Tarawera Ultra-Trail 102k, and has also won races including Lantau 50 and INTHANON 20. His stated career goal is to win a 100km ultramarathon world title.
Notable Wins
- — Lantau 50 2023 (winner)
- — INTHANON 20 2025 (winner)
- — Tarawera Ultra-Trail 102k 2025 (2nd)
- — Western States 100 2025 (10th)
- — SKY HUNTER 50k 2025 (2nd)
Upcoming Races
27 Jun 2026
Follow Hiroki Kai's races in the Crewed app
Download Crewed →