That Time I Got Reincarnated as a Slime Season 4's premiere week delivered the highest opening among new Spring 2026 TV anime, with a 3.1% Kanto household rating. One Piece and Ascendance of a Bookworm Part 3 followed.
That Time I Got Reincarnated as a Slime Season 4 opened Japan's Spring 2026 anime slate with a 3.1% Kanto household television rating during the March 30 to April 5 survey window, making it the highest-rated new premiere of the week. One Piece followed at 2.5% on its Elbaf arc resumption, and Ascendance of a Bookworm Part 3 hit 2.4% on its own premiere.
The Kanto region household ratings, published from the survey week of March 30 to April 5:
Sazae-san: 7.5%
Detective Conan: 6.0%
Chibi Maruko-chan: 5.7%
That Time I Got Reincarnated as a Slime Season 4 (premiere): 3.1%
Doraemon: 2.8%
One Piece (Elbaf resumption): 2.5%
Ascendance of a Bookworm Part 3 (premiere): 2.4%
Crayon Shin-chan: 2.3%
Star Detective Precure!: 1.8%
Animated Curious George: 1.6%
The ratings reflect live Kanto-region household viewing percentages and exclude delayed playback, which underrepresents streaming-heavy demographics that typically rank newer titles higher.
Outside the broadcast slate, Nippon Television aired the earlier Detective Conan: The Scarlet Bullet theatrical film on Friday, April 3, which drew a 7.2% rating, the highest figure for any anime programming in the survey window. The airing coincided with the opening of Detective Conan: Fallen Angel of the Highway in theaters on April 10, a scheduling move that positioned the television re-air as a lead-in for the theatrical debut.
A parallel international weekly audience poll, drawn from an online voter base rather than Japanese television meters, placed Re:Zero Season 4 first at 12.04% of votes, with Witch Hat Atelier at 10.27% and Classroom of the Elite Season 4 at 5.58%. The gap between the two data sources reflects the standard split: Japanese TV ratings skew toward long-running family shows and established broadcast properties, while international polls track a younger, streaming-first audience.
The combined picture positions Slime Season 4 as the strongest cross-audience new Spring 2026 premiere on Japanese television, while Re:Zero and Witch Hat Atelier have the larger international pull.
One Piece's 2.5% rating marks the franchise's first week back after the Elbaf arc's formal premiere on April 5. The series had paused production under Toei Animation's updated seasonal format and returned with a new opening theme, ending theme, and directorial lineup. The Kanto rating is in line with the franchise's average post-break figure and represents roughly the same household share the series held through the Egghead arc.
The ratings picture typically stabilizes by the third or fourth week of a cour. Long-running family titles maintain their floor, while new seasonal premieres drift within a percentage point of their opening. The Spring 2026 top five will almost certainly remain dominated by Sazae-san, Detective Conan, and Chibi Maruko-chan, with Slime Season 4 and One Piece competing for the highest-rated seasonal or shonen slot.
For Indian viewers watching through Crunchyroll, the Kanto ratings are a useful proxy for mainstream Japanese reception but do not track streaming-first demographics. India's simulcast viewership trends are closer to the international poll pattern, with Re:Zero and Witch Hat Atelier drawing the larger Indian audience through the Crunchyroll India catalogue.
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