Rem, the Loyal

Whenever Rem, the Loyal attacks, she gains +X/+0
until end of turn, where X is the number of +1/+1
counters on creatures you control.
Whenever a creature you control with a +1/+1
counter on it dies, put a +1/+1 counter on Rem,
the Loyal.
If Subaru, the Unyielding is on the battlefield,
Rem gains +2/+1.