Not a chiobu perhaps to some but definitely one of the most kawaii-bu
+1 for Ai Fukuhara (福原 愛)
I've been a big fan of hers since the 2004 Olympics where she made her debut at age 15 - the youngest-ever olympic female table tennis player.
She's been playing since age 3, turned professional at age 10. Truly a great story about nurturing of talent.