The ramen at isshindo was fairly standard, and does not seem to be Japanese owned, which can be seen by the menu and food they have.
The spicy tonkatsu broth was not as rich as tonkotsu broth should be, (and fairly mild) and the karaage was more of a general gaos chicken, and slathered with a sweet sauce. It didn't taste bad but not what authentic karaage is. The takoyaki seemed to be reheated frozen takoyaki but otherwise not terrible.
For gluten free, vegetarian, no pork dietary restrictions however they do an amazing job accommodating which you would be hard pressed to find and other ramen shops. If you have dietary restrictions of that sort this place is great.
That being said there are much better, more authentic ramen restaurants in Boston but for a quick cheap bite it's not bad.