Long text. TL;DR at the bottom.

First thing to keep in mind is that this is really the first time I've ever had something more than having a crush based on looks. I'm 22, Canadian-born Asian living in America, overweight (5' 10"-ish and 200lbs. Pretty introverted and quiet, recently trying my best to break out of my shyness shell by studying abroad.

So a quick rundown of the backstory is I'm currently studying abroad in Japan, and there's a girl who came in the same "batch" as me (a group of students come and go each semester). Something about her caught my attention when we did our self introductions, and she was rather friendly and open in general. That was back in October and at the start I didn't really talk much with her as the people from different countries tended to stick together.

The first semester we had a couple of classes together but we sat pretty far apart and again, didn't really talk much. The regular greeting here and there when we'd meet, perhaps some small talk about the class or assignments. As the second semester rolled around, one of the classes we took was a pretty small class, about 4-5 people, and we were in it together. We started talking quite a bit more, more likely than not because of the fact that I was a native English speaker and she was most comfortable with English as her second language apart from her native one, and the others didn't speak too much English.

It was during this semester that I realized we had quite a bit in common, and we hung out a number of times. Although it was always with the rest of her friends from the same country, it was fun and I enjoy hanging out with them too. Karaoke, movie, arcade, going to events around Japan, so on. Kind of regret not taking a seat beside her at the start of the semester. It kind of recently hit me that I might actually like her, but the date of her returning to her country is approaching fast, just a bit under 3 weeks. I've never dated before so I don't know if I actually like like her, or just really enjoy hanging out with her. I don't think she's ever shown any signs that she's interested in me that way since she rarely ever initiates text conversation unless it's to ask about something specific, and being me I don't know how to slip hints to gauge her response. Should I not say anything and just wait for her to leave, not knowing if we'll even get a chance to meet again and forget about her, or say something knowing the aforementioned?

TL;DR 22 year old guy studying abroad, met girl, she's returning to her home country in ~20 days. Should I tell her about my feelings regardless of how unsure of them I am?