The series focuses on Renko Usami and Maribel Hearn of the Secret Sealing Club from ZUN's Music Collection, as their research leads them to explore the backstories for various members of the Touhou cast.
The Sealed Esoteric History contains examples of:
- Ascended Extra: Renko and Maribel are the focus of the series as opposed to Reimu and Marisa like most other Touhou fanime projects. Lampshaded at the end of the first and second episodes where Reimu gets upset that she didn't appear and Marisa has to remind her that they're not the main characters of this particular series.
- The Cameo: Two women resembling Reimu and Marisa are seen during part of the first episode (which amusingly invalidates Reimu's complaints in The Stinger about not appearing).
- Curb-Stomp Battle: The first episode depicts Yukari's attempt to invade the Lunar Capital and well... it doesn't go so well.
- Early Installment Weirdness: It has been stated that the first episode is meant more as an opening for the series than an actual episode, so differences are to be expected later down the line.
- Original Character: The series creates new characters to fill in roles necessary for the backstories of the pre-existing Touhou cast, such as other Lunarians in the first episode to fill up the royal family and infantry, and the second episode introduces Sanae's sister Yayoi so that someone will be able to tell Renko and Maribel about Sanae's past.
- Origins Episode: The main idea behind the series is that it develops the backstories of various Touhou characters based off of canon information and filling in the gaps with original content.
- Product Placement: During episode 1, there is a shot showcasing posters for several Yonder Voice albums, the group that creates the music for this series.
- The Stinger: The first two episodes feature scenes after the credits in which Reimu complains about her absence and Marisa tries to comfort her.