I say take a long break to get your life in order, find your way again, fight this thing bringing you down. Depression isn't easy to shake, especially when you lose something important. So get rest, make a plans for yourself like a long vacation or something you want, and if that doesn't work get help. Call people you trust or talk to people who are familiar with this pain. I'm not experienced with these situations, but I want the best for you so do not give up, not on yourself or your work. Because that would be the worst thing possible.
FNIA Studios says they will help with the project if need be. They have made progress in their own work. So calling on them to help could work. Just try to remember your vision and keep to it. Don't give up.
Please get well Yuuto Katsuki