IJN aircraft carriers in WW2 were equipped with catapults, but the aircraft un use did not use these, as all were light enough to get off the flightdecks, without assistance of the catapults, even when loaded with ordonance. Only the proposed successor of the B6N "Jill", the B7N "Grace" and the N1K1 "Shiden" heavy fighter were propably too heavy to do so, but these never operated from a carrier in the first place, as there simply were no left in operational service, by the time they came around.
A fully laden M1K1 in a fighterbomber role could carry some four AP bombs of 250 kg, where the smaller A6M type rarely exceeded a bombload of a single such bomb. Simmilarly the proposed B7N could carry a torpedo, like the Jill, but alternatively up to two tons of ordonance, where the B6N could only carry 1000 kg at best.