Interior room is 120k cheaper. how bad is no window really?

Pay the 120,000. This is the single most consistent regret we hear from students, and coming from a sunny country makes it more of a risk for you, not less.

What you are actually buying is not the view. It is three things:

1. Daylight. A Seoul winter has sunset at 17:20 and long stretches of grey. If your room has no window you can go days seeing daylight only on the walk to class. People underestimate how much that affects mood and sleep, and students from climates with year-round sun have no reference point for it — which is exactly why it hits them harder.

2. Air. Interior rooms have mechanical ventilation only. Cooking smells from the corridor, damp from your own shower, and the dry winter air with no way to change it. This is the practical complaint people make first.

3. A sense of time. Waking with no idea whether it is 7am or 2pm sounds trivial and is genuinely disorienting after a few weeks.

The arithmetic you are doing is 120,000 x 10 = 1,200,000 won. Set that against: this is the room you sleep in, study in, and retreat to when the month-two homesickness arrives, for ten months. On a total year cost of 15,000,000 to 20,000,000 won all in, it is a rounding error against the thing it affects.

If the budget genuinely cannot stretch, the mitigations that help: a bright desk lamp with daylight-temperature bulbs, a small humidifier for winter, and getting out of the room deliberately every day rather than studying in it.

But if you can find the 120,000 anywhere else in your budget — eat out once less a week, take one fewer weekend trip — take it from there and get the window.