The B-29s switched to night bombing at lower alts in May 1945 (saturation area bombing), making traditional escorting redundant.
Prior to that the VLR (Very Long Range) FGs did escort them from Okinawa for some weeks, both P-51D and P-47N. After the switch to night bombing the FGs went to sweeps over Japan untill wars end in Aug 1945.
The decision to have the B-29 attack at night at more to do with the fact that they could achieve better results dropping from much lower alts (below 10k) and using incindiery, rather than dropping at 30k with regular HE, and dealing with the jet stream over Japan, which caused a lot of problems for accuracy.