There is no in-game tracker to know which ones you have missed so I would HEAVILY recommend tracking them manually or getting them on your first playthrough as you progress through the game. The Shitieshous do "migrate" over to the Hub village once you find them and the achievement tracker works as well to give you an idea of your raw total number.
Also All flags, items and Shitieshou picked during a playthrough counts for the overall play even if you quit the battlefield mid-map (Thanks GoH Sticky for the confirmation!)
Shitieshou are the Snuggly from Dark Souls equivalent of this game: They are meek panda demons that kinda just hang out and will eat an item you drop in return for another item of AT LEAST the same level of rarity so sometimes for example sometimes you can get a 4* out of a 3* item (thanks to Freud & Wyatt for the info). I believe anything can be fed to them but I usually just feed them a random weapon that I don't want. Ensure that you DROP the item, do NOT discard as discarding permanently removes the selected item.
Once you drop the item you will have to wait a few seconds for the Shitieshou to eat it and burp out a trade.
There is a total of 23 of them spread across the entire game. Since you can replay missions at will you do not need to worry about "missing" any of them as well! Below is a video showing all locations(All video credit to 100% Guides):
If you would prefer a text guide:
*** Spoiler - click to reveal ***
- The Valley of Crying Wraiths: About halfway through the mission you will get a Battle Flag that has a decline. Go down the hill and the Shitieshou will be on your right.
- The Demon Fort of the Yellow Heaven: In one of the corner buildings in the village, there's a bunch of pots/crates within there too.
- The Flying Swallow of Heishan: From the first Battle Flag: go through the battlements until you find the huge gate. Then before entering the gate go to the right and search within the wooden structures.
- In Search of the Immortal Wizard: Right next to a Battle Flag once you cross the lake with all the water demons.
- Shadow of the Sacred Mountain: Once you raise the battle flag that was guarded by the Tiger, go down the stairs and you’ll find it in a small wooden alcove on your left.
- Fall of the Corrupted Eunuch: Go to the final flag next to the Temple Entrance. Then you'll need to turn around and find a white ledge that you can climb. The Furry friend will be a bit further along the roof.
- Escape From the Capital: From the second Battle Flag: enter the scroll library and go to the upper section
- The Battle of Hulaoguan Pass: Once you get the Battle Flag in the middle of the Battlefield: move up through the left battlement. When you get to the top go to the right and find the Building opposite of the Ape.
- Centuries of Glory Burned Away: Found in a dead end that is right across from the Golden Cicada location.
- The Lost Sacred Artifact: Once you are forced to go down into the water, you'll find this guy by progressing forward.
- Darkness Over the Hanshui River: Once you go past the gate guarded by two Fanatics. Uncorrupt the Battle Flag, then check the buildings opposite it to find it.
- Tyrant’s Final Banquet: Within the caves, you’ll eventually reach a room guarded by a Crocodile. This is right where it is.
- Fate of the Entertainer: From the second Battle Flag, in the bamboo garden, go to the left side past the statue.
- War’s Flames Blaze Fiercely: About halfway through the mission, you’ll have to kill a spearman guarding a Battle Flag. Once you beat him, go past it and branch off to the left as soon as you can. You'll find this one in an alley to the left once you defeat the soldier guarding it.
- The Uninhibited Heart: Once you get to the room with a lightning-summoning Warlock: Use the pillars in the room to get to a hidden alcove with a long ladder you can climb up. You'll find the lil guy at the top.
- The Way of the Warrior: Once you get to a village: cross the bridge and raise the Battle Flag. Diagonally and on a small edge is the Shitieshou.
- Lu Bu, Mightiest Among Men: Eventually you'll enter a round room with a large statue in the middle. Get to the top and you’ll find an axe-wielding soldier. Once you defeat him you'll find a platform along the back of the statue with the Shitieshou.
- Behold the Glaive of Righteousness: Late in this level you'll get to a foggy area. Once you do, continue along the main path to find a Tiger. Defeat it and then climb up the long ladder and cross the bridge. At the end of the bridge, go left and kick down the shortcut platform. Now climb up the white-painted ledge and head left. Climb up the wooden scaffoldings and head to the rooftop, then drop inside it (not where the Demonized Officer is, but immediately below the rooftop). Once inside, use the broken platforms to get to it.
- The Assault On Wuchao: Found right before a Battle Flag, in the same hallway where you fight against a large humanoid monster.
- Let’s Make Our Armor Shine!: From the second Battle Flag, climb up the nearby ladder to get on top of the boat, then continue down the pier on the other side. Here, defeat the solider and then unmoor the raft. Continue along the pier to eventually climb up a ladder and find the marking flag. From there: continue to the very top of this boat to find the Shitieshou.
- Decisive Battle of Guandu: Once you get to the last Battle Flag after defeating the first boss: drop down into an area below to find the Shitieshou.
- Heirloom Seal of the Realm: At the start of the mission, open the gate and head left. Continue along the street until you can fight a Warlock. Climb up the platform near the Warlock to find an opening. Climb through it, then go to the very end of the other side to find it.
- Let’s Make Our Halberds Shine!: Progress through the mission until you get to a village and then go through the village until you see 3 dogs: the Shitieshou will be behind them.