This incident has just been reported by the YOMIURI SHINBUN (Serious Japanese Newspaper).
JAL flight 2250 departing from Niigata bound for Itami Airport in Osaka took-off without clearance from the tower on the 16th of August. THe plane was an MD-90. It looks like ATC didn't realize it neither.
The plane eventually landed safely at Itami.
This is the second time this year, I'm wondering if JAL is really taking any serious measure in order to improve their safety.
For those who understand Japanese: