You certainly want to improve on your fundamentals, but what fundamentals exactly? Number 1: Head proportions, even when we are looking for a more stylized design is important to have a good foundation on head construction, for this, I recommend to search resouces about "head construction" (yes, the subject specifically goes with that name). Number 2: Form/draftsmenship: this one is a little difficult to explain, but to put it simple, it has to do with the way we draw each mark on our canva. The end result is a drawing that feels plausible, or that exists in its own world and feels 3d. Because is a very specific concept there isn't that much courses that teach that in isolation, sometimes is quickly reviewed in some places, in others is completly overlooked. But their impact truly differentiates a more amateur drawing from a professional one. The best place that I found that teaches that is drawabox.com Number 3: Figure drawing: I assume you would want to draw characters with this style, figure drawing doesn't need anatomy knowledge from starters, it gives you a manikin to begin posing characters. Maybe you are expecting some advice on the medium itself (ink) but believe me when I tell you that the medium can be easily resolved if you already know the fundamentals. Consider the fundamentas as the theory, when you have practiced this enough, the knowledge guides the decisions you make when creating art. By practicing and learning from any of these topics, your drawings will start to gear towards the professional results of Inoitoh, you just have to be patience with the learning process and ask for advice if necessary. Hope this helps with your art journey!