Taking place thirty years after the original anime, Shadowside this time around centers around Natsume Amano, the daughter of Nate and Katie (and the older sister of Keisuke Amano) from Yo-kai Watch: Shadowside - The Return of the Oni King. Natsume and her two friends, Touma Tsukinami and Akinori Arihoshi, are the owners of the new yo-kai watches. Along with Whisper and Jibanyan, the trio go on adventures similar to how Natsume's father used to, but with a catch— these Yo-kai aren't the silly and fun types you're familiar with. They have a "shadow side", which is scary and dangerous, and a "light side", which looks comparatively friendlier.
Shadowside features a less cartoony art-style than the original and is slightly more mature, but it's still as zany as ever. The series is more serious and plot-driven than its predecessor. Instead of three segments, the series will only have one segment per episode.
Yo-kai Watch: Shadowside provides examples of:
- 20 Minutes into the Future: The show takes place in the 2040s.
- Ambiguously Brown: There are a lot more dark-skinned characters in Shadowside than in the original anime. There are also a lot of characters with (presumably natural) hair colors such as blond and red. Considering this takes place in the future, it's possible Japan's population is more diverse in the 2040s.
- Art Evolution: The art-style is less cartoony than previous installments. Yo-kai are no longer nearly as stylized.
- Ascended Extra: Natsume's brother Keisuke was a bit character in the film. In the series he is a major character.
- Badass Biker: Venoct is an example of this.
- Blush Stickers: Keita had them as a baby.
- Cast of Snowflakes: The background characters all have varied and diverse designs.
- Darker and Edgier: Though Lighter and Softer than the prequel film, the anime is this to the original anime. It has an older cast, scarier characters, and a more serious plot.
- Eerie Anatomy Model: An anatomical model named Jinta appears in Episode 5. He's in love with the student Minami. So is Koji, who uses Jinta as the canvas of his love confession because he knows Minami likes the model. It angers both her and Jinta, and when Jinta is shot (twice!) by Fukurou, his negative feelings get the better of him. His shadowside Jingeki, a giant who uses his organs as bludgeoning tools, comes out. Fortunately for all, Minami manages to calm him down. Upon his subsequent Love Confession, she replies that he's already spoken for by her grandmother Machiko, who went to the same school 50 years ago and whose resemblance to her triggered Jinta's new feelings. He melancholically remembers Machiko and needs time alone upon learning that she's no more but thought of him until her end.
- Family-Unfriendly Death: Shutendoji tracks down Dr. Chameleon and strangles him to death in Episode 23.
- Kid Hero: The leads are in junior high school and are thirteen to fourteen years old.
- Kindhearted Cat Lover: Once again Venoct, almost to Knight Templar levels.
- Knight of Cerebus; Almost every time Haruya shows up the plot gets noticeably darker. This comes to a head in episode 23 when he kills the Monster of the Week.
- Jorogumo as well, given that she had Haruya wrapped around her finger the whole time she was using Ayame as a vessel (with Ayame not suspecting anything) and ridiculing him with her requests, ordered him to kill another Monster of the Week, and defeating several heroic Yo-kai with little trouble.
- Soranaki tops him easily, as after being defeated in the fifth movie, he returned to try to bring chaos on the world once again. And the Youseiken Haruya and his cronies were gathering in order to awaken the Princess? They were meant to awaken him instead.
- Not Evil, Just Misunderstood: Most of the Yo-kai don't mean the trouble they cause. They basically just lost their self control and a tragic backstory to explain how they became a Yo-kai and their shadowside forms rampage. Once defeated, they mellow out and help the cast.
- Retcon: It’s established in Yo-kai Watch 2 and the first movie that Nate’s grandfather created the first yokai watch, yet not only does the movie begin by basically disproving that stating that the Yokai Watch was created in ancient times but it doesn’t mention nate’s grandfather at all. The whole Lightside-Shadowside power was never mentioned in the original series, but was apparently present in the original series' timeline even appearing in Yo-kai Watch 4 as well in the 1950s.
- Shout-Out: When Whisper uses a face changing app on a smartphone, the resulting pretty boy face looks suspiciously like a Palette Swapped Gilgamesh.
- Spin-Offspring: The anime stars Nate and Katie's son and daughter.
- Two Guys and a Girl: Akinori, Touma, and Natsume.
- You Don't Look Like You: Due to the Art Shift to a somewhat more realistic takes on Yokai, almost all of the returning Yokai don't resemble their previous designs. Whisper, Komasan and Komajiro (subverted with the Komasan and Komajiro appearing in Shadowside, as they are different individuals from those of the original series) are the biggest offenders.
