Kirito, the Black Swordsman

Partner with Asuna, Lightningflash
When you put one or more +1/+1 counters
on one or more other creatures, put a +1/+1
counter on Kirito.
While Kirito has five or more +1/+1
counters on him, he has double strike.
"The main reason I got stronger was so I'd be
able to survive."