Gintama: Gintama. - Slip Arc

Season overview

Task: Write a JSON object for "Gintama" Season 9.
Keys: overview (160-220 words), primer (array of exactly 4 concise bullet points).
Constraints: Use only provided synopsis and sources. No invented facts. No markdown/asterisks/headings/bullets in the text (though primer is an array). Output valid JSON only.
Target: Season 9 (Porori-hen).
Synopsis:
Context: Follows grim events of Iga, Kokujou Island, Rakuyou, and confrontations with Tenshouin Naraku and Tendoshuu.
Season name: Porori-hen.
Theme: Trip down memory lane, Yorozuya doing odd jobs.
Plot point: Umibouzu returns to Edo, is livid about Kagura having a boyfriend, blames Gintoki for being an incompetent guardian.
Tone: Shameless parodies, risqué humor, lively camaraderie, hilarious and emotionally stirring situations.
Characters: Gintoki, Kagura, Shinpachi.
Sources:
[1] TMDB: World where aliens invaded Edo Period Japan; skyscrapers, trains, motorbikes.
[2] Wikipedia: Based on Hideaki Sorachi's manga. Produced by Sunrise.
[3] TMDB Cast/Crew: Gintoki Sakata is Yorozuya Gin-san, a man with the soul of a samurai.
[4] Variety: Serialized since 2003.
[5] IMDb: Aliens invaded feudal Tokyo; unemployed samurai finds work.
Overview (Goal: 160-220 words):
Following the grim events of Iga, Kokujou Island, and Rakuyou, as well as multiple fruitless confrontations with the Tendoshuu and Tenshouin Naraku, Gintama Porori-hen shifts focus. This season takes viewers on a trip down memory lane to a time when the Yorozuya were primarily focused on performing odd jobs. The narrative features Gintoki, Kagura, and Shinpachi facing unforeseen situations that are both hilarious and emotionally stirring. A significant plot point involves the return of the great space hunter Umibouzu to Edo. Upon his return, Umibouzu is livid to discover that his daughter, Kagura, has a boyfriend. He directs his anger toward Gintoki, accusing him of being an incompetent guardian, which raises the question of whether it is finally time for Gintoki to let go of his daughter. Throughout these episodes, the series maintains its signature style, incorporating shameless par