4 or 5 hours probably, give some breathing room for immigration and traffic on the bus (if you're going that way).

If immigration is bad and takes ~1 hour (not unheard of) then 2 hours on the bus then that's going to start rubbing uncomfortably up against your departure time with less than four hours.

Assuming you're arriving early in the morning off of ANA (~7am?) and planning to head out at 11am? Train could be a bit faster and more predictable to save you some time but will be annoying if you have bags.