I have made tonkatsu and it's awesome! Not dried out or anything (hard to do with pork). Also, it turns out you can totally substitute Tonkatsu sauce with Okonomiyaki sauce and it will still taste great!
The only bad news is that I was super lazy after work and instead of going to buy a new bottle of tonkatsu sauce I just used an unopened okonomiyaki sauce we had in the cupboard that expired last March. If I die, it was delicious. I figured since it was unopened and air sealed, it's probably fine, right? (Probably not)