NyaHiryu Oni is a Portugese fangame made by Fish Oni where the player controls a Let's Player StriHiryu on a quest to find out whether or not the Oni really exists or not. The game has a unique chase system not used in other Oni games where you can only lose the Oni by hiding in the closets scattered aroud the mansion. Before you found a closet, you would have to do something else to lose the oni, like bracing doors and so what.
WARNING: This section and the following one contain spoilers. StriHiryu hears about a mansion on the outskirts of town and heads there with KyoKoon and PianoDream to find out whether the Oni exists or not but when they arrive, Kyo pushes Stri into the mansion and the door shuts behind him. As he explores he finds that the Oni does exist and that Hiroshi, Mika, Takuro, Takeshi and a cat are trapped in the mansion with him. He finds that the Oni had dropped the Switch Room key, he travels to the room and finds a note. It will say "Up is Heaven, Middle is Earth, Down is Hell" which is a reference to HetaOni. If Strihiryu pushes the switch down, the mansion will explode killing StriHiryu. IF Strihiryu pushes the lever UP, A rope ladder will fall down and guide him to the safe room where he will meet Mika. Trying to persuade her to come, she refuses leaving Strhiryu on his own. he heads back to the lever room, puts it back in the middle position and a key falls out from the ceiling. This key leads up to the bedroom where Strihiryu will meet Hiroshi. He wakes him up and asks him to join him, but Hiroshi refuses, instead he gives him a first aid kit and falls back to sleep. Strihiryu finds something shiny in the back of the room but upon grabbing it, the oni comes out and chases him. StriHiryu runs back into the safe room and hides in the closet, luckily the oni doesn't find him making the coast clear. He heads to the bedroom again and pushes a bed to the right and discovers a hole in the floor, grabbing a bedsheet he decides to climb down. But the bedsheet is too small and he slips and falls into a white room, grabbing a red doll, a blue doll and a yellow doll he finds a note descrining an ancient ritual, this gives a clue to the player by the text saying "Black Table", he leaves the white room and hears a door unlock. He then goes to the BLACK room where the black table is and he finds a black cat, asking the kitty to come it refuses but StriHiryu realizes he grabbed a fish in the bathroom, he gives it to the kitten, thus makes the cat to join him. Luckily, the player now has the ability to save the game due to the cat being with the party. He then finds the black table and kills the dolls on the table, and then he finds a padlock on the floor but the oni appears AGAIN and begins to chase him.
Coward: StriHiryu starts to wimp out and decides not to enter the mansion after all. Kyo calls him a coward as they walk away.
Rape: StriHiryu attempts to open a door over and over but when he succeeds the Oni is waiting for him and it eventually catches him.
Fool: StriHiryu destroys the dolls over the white table but when he tries to leave the room, it starts to heat up. He looks around, trying to find an exit but has no luck and dies.
Betrayal: StriHiryu, deciding against Mika's will, refuses to kill the spider and instead lies to her and says that he saw Takuro before. She doesn't believe him but goes along to be safe, but when the Oni comes after them, Mika sacrifices Stri and runs back into the safe room.
Escape: StriHiryu finds a subway station in the laboratory and enters it with the cat in an attempt to escape. Stri then after overcoming the fear of the carrige going berserk and the cat's claustrophobia, he finds himself in a 404 zone and heads home from there, looking back over the adventure.
Hero: StriHiryu, angered by the deaths of Hiroshi, Takuro, Mika and Takeshi, decides to kill the Oni once and for all by blowing up the the mansion. He activates the detonation system but finds the cat is still downstairs with the Oni. Stri then saves the cat from the Oni but is too battered to escape the mansion in time and is caught in the blast. StriHiryu dies along with the cat.
Nightmare: StriHiryu, angered by the deaths of Hiroshi, Takuro, Mika and Takeshi, decides to kill the Oni once and for all by blowing up the the mansion. He activates the detonation system but finds the cat is still downstairs with the Oni. Assuming he won't be able to save the cat and get out in time, he escapes without it and wakes up in a hospital and returns to the mansion to find the cat is dead.
Dream: StriHiryu, angered by the deaths of Hiroshi, Takuro, Mika and Takeshi, decides to kill the Oni once and for all by blowing up the the mansion. Stri hides the cat in the safe room, traps the Oni downstairs then sets off the detonation system, escaping in time with the cat. After escaping Stri and the cat find themselves in a snowy forest with a single path which they take. They then find themselves in a church where an angel congratulates StriHiryu in saving the cat and promises to make his life very lucky from then on. He then wakes up and finds out it was all a dream.
Unlike most Oni games, this game doesn't follow any chase tropes set by other Oni games. In this game the Oni runs faster than you do but you can still outrun him. Also hiding is your only option to get away from the Oni and even then if you hide in the wrong place he'll find you. Due to this nature all chases are scripted.
Immortal Stri glitch: If StriHiryu's HP drops down to 0 while the cat is in your party, you won't get a game over.
Pre-light glitch: If you save in the lab before you obtain the light key and turn on the lights and reload your save file, the light will be on when you load it up again. This fixes itself if you leave the lab.