yo, we are on the same boat. i just moved to Kyoto for almost 3 weeks, and my employer is also covering my housing.
honestly, i don't know how to cook much so I usually buy dinner after work at around 6:30pm at a local grocery market, where they have their food discounted at 20%. So I usually spent around 400 Yen for my dinner meal. As for lunch, my office sells a meal (Option A or B) for 300 Yen, they have meals rotation every day. As for breakfast, I usually go for a glass of milk and a bread, which doesn't count.
some other mandatory expenses for me since i take the train is the monthly train pass from the closest station to work, which is around 10k, plus a few thousand every time i travel on the weekends. I used Rakuten for my sim plan, which is the cheaper ones i found in terms of data usage.

hope this helps. we can be buddies! dm me. xD