I couldn't finish 'em. Looks like this's gonna get complicated.
It counters all attacks with Flare and can attack normally by inflicting Confusion via Glare on one party member. They will generally be the last enemy alive in any given group, and care should be taken care when dealing with them. Izayoi should be on healing duty, and if she is unable to keep up with the healing duties, have another character should join in to keep everyone alive.
Killing Bug will guaranteed to reward one of its item drops.