Rough video tutorial by neon wir

It's an absolute mandatory mechanic to learn while optimising soul management. The game never tells you about Issen or how to do it. The bosses in this game cannot be Issened, except for the 2nd Marcellus.

[section=Types of Issen]

1- Strafing strike: The strafing happens automatically. Samanosuke will use this to counter most of the enemies' attacks, especially overhead strikes. After quickly positioning himself besides/behind the enemy, he will do an overhead slash with all the weapons, except for the Shippu, where he swipes it horizontally from left to right.

2- Rising Slash: Samanosuke slashes upwards. He'll use this to counter aerial strikes. He also uses this to counter horizontal attacks by crouching low, followed by the rising strike.

3- Dash Slash: Samanosuke dashes forwards and slashes horizontally from right to left. He uses this to counter some of the enemies' attacks, but he will automatically execute this if you did a Hajiki Issen. This is the most favoured move to kill multiple enemies due to the way it's executed.

Kaede has a unique Issen move that's performed differently. During the attack stance while facing an enemy, press forward + attack to flip behind them then press attack after to finish them off. Below gif demonstrates how it's done by BOWIEtheHERO. hinge also managed to perform that finisher successfully during his run.

[section=Glitches]

Missing the enemy It's possible to miss the enemy sometimes. It usually happens when you're too close or you're in a small area surrounded by walls and obstructions. This can also happen if your character strikes high when the enemy's crouching low, or hitting low when the enemy's flying high, etc.

Enemies die by just touching the weapon There're some weapons with a few glitches that actually benefits you. Due to the way they're shaped or the way your character handles it during Issen, you might kill more enemies than you'd expect. For example:

Enryuu: If there's an enemy right behind Samanosuke when he's performing the type 1 Issen, they'll get hit by the Koen when Samanosuke is raising it over the back his head, ready to slash.

Shippu: Samanosuke can kill enemies in front and behind him with the Rising Slash attack due to how he swings it upwards in a circular pattern. Due to it's dual blades, the Shippu can kill a lot with it's type 1 Issen (strafing followed by a horizontal slash).

[section=Myths]

1 - You don't have to lock-on with the R1 Button for increased success chance 2 - You don't have to face the enemy for the Issen to work 3 - There is no timed Issen and a strafing Issen

I'd highly recommend making a save file for both first and second part of Kaede's walk-through. You should do practice it against zombies or Three-Eyes/Dark Spiders first for execution consistency before trying it out on Volchiman.