I also spent a couple of days in Waikiki on Oahu at the tail end of my trip to Hawaii. Much of the food available in Waikiki is either expensive and seafood/steak related (lots of fancy sushi), or a chain (California Pizza Kitchen, Cheesecake Factory, Subway etc), or simply not vegetarian friendly ("authentic" Asian, mostly Korean, Japanese or Chinese, hole-in-the-wall type places). And so it was with great pleasure that I discovered "Mapo Tofu Ramen" on the menu at the Japanese restaurant Gyoza No Ohsho in the bizarre but somewhat pleasing King's Village.
I asked the waitress if it could be made vegetarian, and after telling me that it beat the whole point, (I gently persisted with the greatest politeness and kindness, what other option is there for a vegetarian in a meat world?), she conceded that they could indeed make it vegan (water instead of chicken stock, no pork). Excellent!
I love a good bowl of tofu noodle soup, and this was not disappointing. The tofu was in a glossy, spicy tasty sauce and the noodles were hearty and perfectly cooked. I added some spiced oil, some nanami togarashi (mixed ground chili peppers), and some white pepper from the condiment tray and I was in heaven. The bowl cost a little under $9 without tip or tax.
I think I've found my Waikiki mainstay!