[DreadBringer]

So the culprit is Kiku, the grandma, and she had some connections with Museum. She wants the best for her family, but only them, while as she said she had many bodycounts as well as taking fortunes to make Kagamino family the way it is. Though the bride competition wasn't a front, it's actually a bride competition, just that, Kiku meant for the wife to continue Kagamino shady dealings. Even the bride's homicidal tendencies are her fault too by making Alcohol Memory worked that way. She also died in her burning mansion... just like Ryubee, and as a High Dope, she's the first one to force W to use Xtreme.

The Dopants mostly aren't killed after they're beaten, but Shotaro's concern of their human form is highlighted here due to Kiku being old, of which otherwise, she's far more capable as the Alcohol Dopant than the others. So it seems to save others better, more power is required, so the fight can end faster as Shotaro wanted. This is a case where I got a bit annoyed by Shotaro though (of which, Kiku claims there should be limit in kindness), to kinda justify what Kiku does due to how it's for the best of Kuya (he still should save her, but not correct her behavior).

He failed anyway, due to Tadashi Kimura, the butler, which sets the mansion on fire after her defeat. Loyalty isn't always a good thing, and it's shown in Kimura who'd also support Kiku's dirty dealings. In contrast to what he said to Tokime in their feud, Philip here delivered the truth to Shotaro, but in civil way, that even as Xtreme, there are still something they can't do.

Other than the baddies, seems that everyone that got involved in the bride selection now become friends. And even with a bunch of pretty girls at the bride selection, the male Kuya can become bros with Shotaro too. I kinda wish that after Kanna thanked Shotaro, Shotaro would also brought up that Kanna saved the detectives first too.

Despite being the head family, Kuya's not only someone completely innocent, but can't drink alcohol at all too. Too bad for the others that, it's unintentional, but Kuya could've solved the case faster if he told them that he can't drink alcohol. Kuya's genuinely locked out of the loop of his family's shady dealings, but I'd bet if this is real world, Kuya would be demonized for being a part of Kagamino, or letting them do their shady dealings unchecked, or just being out of touch (when people aren't omniscient, though Kuya wanted to work this off by becoming self-made man).