Hifuunote Nightmare Diary ~ Violet Detector is a video game created by Team Shanghai Alice for Windows computers in 2018. It's the 16.5th videogame installment in the Touhou Project franchise, a direct follow-up to Sumireko's scenario in Touhou Hyouibana ~ Antinomy of Common Flowers.
Sumireko Usami finds herself trapped in a nightmare in which characters from previous games attack her with danmaku. She must survive three weeks and take pictures of the bullet patterns on her smartphone.
The game continues the "Danmaku photography game" format started by Touhou Bunkachou ~ Shoot the Bullet, but adds a teleportation mechanic reminiscent of Impossible Spell Card. The presentation is also more modern, with Sumireko taking pictures on her smartphone and adding tons of hashtags. There are new bosses from games 15-16 as well as final and EX bosses from other games.
This game provides examples of:
- Continuity Nod: The Spell Card names of Week 3 all reference the names of various Touhou games.
- Damn You, Muscle Memory!: It's not C that teleports you like you would think. You actually have to press Shift twice.
- Dual Boss: Satono Nishida and Mai Teireida appear together for the last scene of Wrong Wednesday. Later on, Nightmare Week is made up completely of dual bosses, with each day featuring four characters, which form all possible pairs over the course of the day's six scenes.
- Enemy Mine: In the second scene of Nightmare Sunday, Byakuren and Miko, who are usually enemies, team up against you.
- Extreme Close-Up: If Sumireko is very close to a boss in a photo, she responds with #EXTREMECloseUp.
- Eye Scream: If white Danmaku is taking up most of the photo, Sumireko responds with "#MYEYESSSSS".
- Get a Room!: If two boss sprites overlap each other in a photo, Sumireko responds with "#GetARoomYouTwoLOL".
- Gratuitous English: Has more English in the title than most Touhou games, where it's normally reserved for the subtitle (albeit "Nightmare Diary" is spelled in katakana).
- #HashtagForLaughs: Photos now get hashtags depending on what's on them.
- Hating on Monday: When selecting Wrong Monday, Sumireko says it's so depressing and she wishes there'd never be another Monday.
- Laser-Guided Amnesia: For reasons unexplained, Sumireko forgets the events of the game afterwards. However, the photos she took are still saved on her smartphone. Later in The Grimoire of Usami, she admits she doesn't remember taking them.
- Lampshade Hanging:
- After taking her first pictures of Remilia and Flandre, Sumireko questions how they managed to show up in them.
- Sumireko points out that "Danmaku for Killing with Certainty via Nightmares" would've been impossible if she couldn't teleport.
- Mythology Gag: In Stage 6 of Wrong Sunday, Sumireko compares Nemuno's knives to Pop-Up Pirate ones, a reference to Uwabami Breakers.
- Recycled Soundtrack: In a rare case for this franchise, only half of the soundtrack contains original tracks. The rest are taken from elsewhere.
- Social Media Before Reason: Sumireko seems more concerned with taking pictures for her Instagram than participating in the actual danmaku battles.
- Teleportation: Sumireko being able to teleport has already been established, but it's a major mechanic here.
- Tomato in the Mirror: Doremy initially states that the reason the Dream Land denizens are so hostile towards Sumireko is that they are jealous of her "flesh-and-blood body," which changes context later, when it is revealed that the Sumireko you've been playing is Dream Sumireko, who has hijacked the real Sumireko's body. They aren't jealous just because she's a real person, but because she's a dream-self who somehow managed to Body Swap with her real-world counterpart, something the repressed dream-selves are eager to repeat after the Perfect Possession Incident.