There is no Oni marriage proposal custom, Lum made it all up.
When Mako tells Lum about her plan to con Jariten into dating her by telling him that refusing would be a capital offense under Japanese law, Lum calls her "a true kindred spirit". (Lum telling her relatives and alien friends that the proposal thing was an Earth
custom could account for Rei showing up later, and would explain why Mister Invader always seems so perplexed whenever he sees Lum and Ataru carrying on—he thinks it was Ataru
who insisted on the "marriage".)
- Wasn't it more of an "If you grab an Oni's horns you get a wish." kind of deal? And when Ataru screamed about how he could finally get married while holding Lum's horns, she took it the wrong way?
- This troper remembers it was more like than a "Spoils of war" scenario. While Lum's father originally intended to invade Earth, in the end Eartheners and Oni boiled the conflict down to a contest between two single champions. Then Ataru won, loudly bragging about being finally able to get married. While the reader knows Ataru was speaking about Shinobu, Lum and her family had no way to know that bit of information. As far as they were concerned, the invasion failed and the Chosen Champion of Earth, after proving his superiority to the Oni Race, asked their princess in marriage. Basically Onis, as the losing part, owed Ataru, and since he asked Lum in marriage, they thought that understandable and desiderabile. By the time Lum found out Ataru was nothing like a hero and a champion, she had already fallen in love deeply with him.
appeared as a Tomobiki High student (in the same class as Ataru!), after all, and we know that Shin and Juria are Kenshiro's childhood friends... Only, we never saw them because they're in different classes (maybe even the same). Also, Jagi is another Tomobiki High student a year above them and Raoh and Toki are former students because Ryuken lives in the area, and enrolling his adopted son at the same school was easier than enrolling them at different schools.
- It would explain the lack of delinquents at Tomobiki: with Kenshiro, Shin and even Jagi around defending the meek, who would dare to be a bully?
Ryunosuke's mother is not better than her husband and Ryunosuke should not miss her.
The manga clearly states that Ryunosuke's mother abandoned her husband. We can guess many
reasons to NOT want to remain with Fujinami, but why she would leave her daughter behind? Either she thought that Ryunosuke would be better off with her father for some reason... or she did not care leave her daughter with that loony.
There not only are giant robots, cyborgs, aliens and spaceships in this universe, but also several characters (Ataru in a Sakura's dream; Azusa...) use the Rocket Punch
or a variant, quoting Kouji Kabuto
verbatim. So that the mazinwars
happened several years before the show -and humanity learnt how building mecha during the conflict-. And that was because the Oni invaders chose challenging humanity to playing tag instead of invading Earth directly: they had seen what had happened to the Vegan Alliance
and not wished sharing their same fate.
- That explains as well why nobody is -too- fazed with all the craziness surrounding them.