A runner makes a run and first hits sensi. They do not break the subrutine. Next they hit Janis and can't break any subrutines. What happens?

Do they only take 1brain damage because after that the run ends?

Sensei puts an End the run subroutine after all the subroutines of Janus. So if the runner didn't break anything, all four Do one brain damage subroutines would happen, and then the End the run subroutine.

Goreshde said:

There is no entry for Sensei in the FAQ, but given its cost and effect, the most reasonable interpretation is that " after all its other subroutines " adds one subroutine at the end of the list of subroutines, rather than one subroutine for each entry in the list of subroutines. If you think that's incorrect, I suggest emailing Lukas.