Hmm, that seems to parallel Mariko Nanba somewhat. She dropped out of the composition scene about the same time as Kumatani, and her Facebook profile does make it very likely that she was married to Tomoya Ohtani.
I don't think Nanba was confirmed to have left SEGA, but she is under what seems to be the "non-SEGA" section of sound creators for MARIO & SONIC AT THE OLYMPIC WINTER GAMES on the DS. Kumatani is there as well.
The difference of course being that Nanba seems to have returned to sound design, what with Space Channel 5 VR: Kinda Funky News Flash! and The Rub Rabbits!/Kimishine & Akadoko LIVE+. Perhaps it's possible Kumatani will return as well, but it seems silly to think the parallels would run forever.