Sensei Golden-Tail

Bushido 1 (Whenever this creature blocks or becomes blocked, it gets +1/+1 until end of turn.)
{1}{W}, {T}: Put a training counter on target creature. That creature gains bushido 1 and becomes a Samurai in addition to its other creature types. Activate only as a sorcery.

The List

Champions of Kamigawa

Bushido 1 (When this blocks or becomes blocked, it gets +1/+1 until end of turn.)
{1}{W}, {T}: Put a training counter on target creature. That creature gains bushido 1 and becomes a Samurai in addition to its other creature types. Play this ability only any time you could play a sorcery.

Note that multiple instances of the bushido ability each trigger separately.

The training counter just marks which creatures have been changed; an effect that removes the counter doesn’t change the creature’s types or abilities.