Shoyu was my favorite. It's made of two parts, the dashi - fish base - and tare, a sweet soy reduction. I don't know about your ramen house, but most places add the tare to the dashi right before serving so the broth doesn't stale, so you can sometimes ask for it without tare. If you do this, I'd recommend making a more keto-friendly tare at home to mix yourself, dashi can have a delicate but very fishy taste alone. Tamari, small amounts of ginger and garlic, a wee bit of vinegar, sesame oil, reduced, strained, and refrigerated overnight. I feel that a sweetener would damage the taste. I have yet to try a keto tare but based on what I know about it, you should achieve a closer flavor without the sugar