Fumiko the Lowblood has bushido X, where X is the number of attacking creatures. (Whenever this creature blocks or becomes blocked, it gets +X/+X until end of turn.)
Creatures your opponents control attack each combat if able.
Fumiko’s ability doesn’t force an opponent to pay for effects in order to be able to attack with their creatures (such as Ghostly Prison, for example).
Fumiko’s ability doesn’t force tapped creatures or creatures with summoning sickness to attack.
X is variable. The bushido bonus is calculated each time Fumiko’s bushido trigger resolves, based on the number of attackers at that time.