CirKills move around the enemy's side in a circle, firing at MegaMan whenever he steps onto their row. The best way to deal with these is to use the ElemIce chip on an ice panel, and doing this usually gives a counterattack when done correctly.
Deleted CirKills yield the Circle Gun (サークルガン,Sākuru Gan) series of Battle Chips. When used, a target reticule circles the perimeter of the enemy's side. Press the A button to stop the reticule, attacking the targeted panel and the next three panels in sequence. These chips are cursor-type. As the CircGun is of a higher level, the damage increases and the target reticule will be faster. This chip also appears in Mega Man Battle Network 5 and 6, even though the CirKill virus does not, its picture being darkened and causing 100-150 damage.
In Mega Man Battle Network 5 there is a Dark Chip named Dark Circle (ダークサークル,Dark Circle) that works the same as the other variants, except this one targets seven panels rather than four and inflicts 300 damage; stricken enemies also take 50 damage when the Custom Screen opens. However when used, MegaMan permanently loses 1HP and a bug occurs that causes him to lose 100 HP when the Custom Screen opens.