The co-op missions, called "Slayer Missions," are completely separate from the single-player campaign, and even the single-player Slayer Missions. Before you can select a co-op mission, though, you have to progress through the story enough to be given full access to Mahoroba Village, and then you have to set up a co-op lobby/HQ by using the Portal Stone. Once the lobby is created, you can speak with the appropriate NPC to take on one of these tasks. The co-op missions are divided into different phases, 12 total, with the requirement to complete certain ones (indicated with red text) before you can advance to the next phase. These missions are the main selling point to Toukiden 2: teaming up with a group of friends and taking down larger foes, one body part at a time. You can fill in empty player slots with A.I. companions, who take care of themselves pretty well and are fairly skilled at hacking off oni limbs, but nothing beats getting a group of four friends together to work out a strategy for felling a mighty foe.
These missions vary greatly and increase in difficulty with the phase number. Lower phases have players facing groups of small and medium ones, or perhaps one large oni. Things start to escalate around phase 4 when you start facing off against two or three large oni at once. From phase 7 onwards, “Expert” versions of the large oni are introduced as well, which are tougher versions of the ones you’ve previously fought with some new attack patterns tossed in there to keep you on your toes.
Along with the co-op missions, there’s an endless mode and a challenge mode (available in both single-player and co-op) available to test your oni-slaying capabilities via the “Ruin Exploration” missions. The endless mode lets you and your oni slaying crew tackle an unlimited number of floors (and oni) with the option to call it quits every five floors. Every floor pits you against a random oni, or group of oni, so you never know what you’ll face. The one guarantee you have is that it will get harder the further you go and that if your group should ever get wiped out, you’ll lose all of the materials you’ve earned thus far. There’s a definite risk/reward balance to be struck with “do we go another five floors, or take our winnings and go home?” The challenge mode is capped at a max of 10 floors and, again, every floor pits you against random oni. The difference between this and the endless version is that you have to complete all 10 floors before you can leave. Both of these modes provide some great variety to the co-op play and really ramp up that feeling of need to strategize and work together as you don’t have the luxury of knowing what you’ll be going up against ahead of time.
Despite the campaign and open world aspects of Toukiden 2 being limited to single-player only, there’s a lot to do within the co-op only side of things. It’s also a lot more fun to strategize and plan out your build with a group of friends than it is to do that alone. Thanks to the “Ruin Exploration” missions, too, there’s more to do than just grind for materials/gear, though it’s hard to avoid some of that once you start getting into the “Expert” oni missions. Of the handful of Monster Hunter style action-RPGs games I’ve played, this is the one I find myself drawn to the most; the one I enjoy picking up and playing, even if it’s only for a couple of quick missions.