Go out exit 3 and go west toward PNU. Make sure you're walking away from the canal (Oncheon Cheon 온천천).
In just a few minutes, you'll come up on a decent sized intersection. Look for the Starbucks on the SE corner of the light. Caddy corner just a tad southwards to it is Busan Bank, situated on the NW corner.
If you look up across the street, on the very top floor (5th floor) of the SW corner, and you'll see the large neon sign for the Jiu Jitsu Lab in red and white, and black.
So, in the same building of the Jiu Jitsu Lab, there's an ABC Mart (1st floor), Italian Bistro (2nd floor), and Love of Busan (4th floor).
Check out the Lab Mon-Fri
Walk-ins are welcome anytime, though calling ahead ensures Professor Aidan can give you some face time to give you all the info and tools you need to get started on your BJJ journey at the Lab