Three days of falling is a bit much, even for fantasy.
Let's first assume that the Other World isn't Jupiter-sized, or something, since it's a terrestrial body, and the MC hasn't commented on the significantly heavier gravity there. If it's about the size of Earth, that puts it at a little less than 13,000 km.
Terminal velocity in a head-first dive is about 240-290 km/hr. Since he's going feet-first, wearing his normal clothing, and isn't shown to be doing anything to increase his speed, let's go with the low end of that as a conservative estimate. The numbers get even worse if we go faster than that anyway. 240 km/hr for 24 hours per day, for three days, is 17,280 km. That distance would put him falling all the way through the planet, out the other side, and shoot thousands of kilometers back into the air.
Even if he only fell for a bit more than two days that's still sufficient for him to emerge on the opposite side of the planet, though drag from the air would mean that he'd bob back and forth inside that planet-wide hole for quite a while.