[pilcrow]

Summons are put to the top of initiative the round after their summoner dies during a 1v1. This probably also happens in other situations (ie taking out the last member of the enemy party, but not their summons)
The functional result of this is that the turn order goes:
attacker > summons > (new round) > summons > attacker

[renowner]

Supposedly its not a bug, but a feature even if I disagree with it.
Summons always go in the same place in turn order. . .
So when two summoners fight, I've had my 7 youkai move after their 7 youkai. And if the enemy moved last in a round, they aren't allowed to move first in the next round, so then the Youkai move up.

[Neus]

Well, the way the turn order currently works is that minor units (summons, usually) don't shift the party who gets a turn.

I'm making an adjustment to turn order in 3.03 v6 where if the first unit to act for a party is a minor unit, it'll apply round robin. This should help in cases where you beat a summoner and their youkai are still up, or when the summoner gets back up but goes after their youkai.