phd - How should I tell my professor that I want to quit my integrated program midway?

I'm currently enrolled in an MS/PhD integrated program (computer science) at a university in Korea and I just started my first semester. My undergrad is at the same university, by the way.

I've always wanted to go to the US for graduate school and took the GRE and everything, but realistically looking at things it was highly unlikely that I'd get into a good program or get funding, which was pretty important to me. That's when I found out about this lab and the professor. I got in touch with the professor and decided to start out as an undergraduate research intern. Everyone at the lab is amazing (very nice, helpful, well-experienced) and the professor is also a nice person.

When I first told him that I wanted to go for my PhD in the US, he advised that from his and the lab's perspective, they usually prefer integrated program students over regular master's students as they're usually at the lab for a longer period of time. I expressed my wishes to receive my master's here and go for a PhD abroad, and he strongly advised that I just finish the entire PhD program here and go for a postdoctorate position abroad.

All of this didn't seem like such a bad idea at first, but I'm starting to slowly realize that this lab may not be the place I want to receive my PhD from - and it's only my first semester.

First off, I'm sure that many professors and advisors out there are the same, but my professor has his own personal research interests and tries very hard to "nudge" (i.e. force) students to work on those projects. This isn't too terrible, I suppose it's how labs work, but the problem is that those interests aren't the same as mine and it's stressing me out quite a bit.

For a bit more detail, the lab I'm at works on deep learning algorithms and applications. When he advertises his lab (he did this to me) he always says that the lab does a variety of research (e.g. bioinformatics, social media analysis, finance, NLP, etc.) and that if you enter the lab then you'll be surrounded by people who are great and have similar interests. His main field of interest is bioinformatics and drug development using AI, and I've recently been semi-forced by him and another PhD student to participate in a project despite me having absolutely zero background knowledge in the material and not wanting to do it.

I've had thoughts of just staying in this lab until I complete the PhD portion of my program (our school allows you to quit midway and receive your master's if you fulfill the requirements) but these days the thought that I need to go somewhere else is becoming increasingly more imminent. In my mind, a PhD is something where you receive guidance and counsel while pursuing research in a specific subject. If my advisor's interests don't align with mine I have a feeling I'd be setting myself up for something disastrous.

I'm still in my first semester, and so I have about 3 more to go and have plenty of time to work hard and plan things out. I'm curious though, how should one normally approach this kind of issue? My largest fear is that he would be very reluctant to let me go and may write a subpar letter of recommendation for me.

Thanks in advance. Any tips or opinions are greatly appreciated.