welcome to the forum
first question (you may want to jump to the second question): does the grafted trunk bother you? My katsura was grafted high up on the trunk like this, and this drove me crazy to the point where i was losing sleep over it.
You may want to reach out to the person who had the same type of tree as you, and the same 'issue' (if you consider it to be one):
https://www.bonsainut.com/threads/mikawa-yatsubusa.21519/page-2
One way is to air-layer above the graft, but this can be risky and disappointment is something you want to avoid with your first tree.
second question: how much reading/practice have you done, and have you visited a local nursery? Are you familiar with your local club(s)?
my recommendation: This is your first tree, and it will not be your last tree (hopefully), nor will it be your masterpiece.
i would recommend that you simply get used to keeping it alive for a full year. There is a lot to know just with regards to watering, fertilizing, and overwintering.
I was very thankful that somebody recently told me about the Mirai videos (esp. spring fundamentals, fall physiology), which are free. These videos completely advanced the way I understood trees in general.
Once you've watched these videos, start spending a lot of time on this forum, and read through threads carefully and take notes.
When you rewatch those Mirai videos for a second time--say, six months from now--you're going to be astonished as to how much you missed the first time.
your tree: take it to a local bonsai nursery, ask about winter care in your climate in particular. ask if somebody would be wiling to sit down with you next spring and repot the tree with you. You will learn a lot in that hour through conversation.
