Wait... the landlady's name is Masu too!! Just like the cook in Harlock 1978!
And with this one shot epilogue, we now have a full name for her. Masu Yamata. All this time I figured she'd be named the same as her Harlock counterpart, but wasn't 100% sure. This at least confirms it!
Also, this third(?) generation descendant of Nobotta is named Orita Oyama. Kinda the opposite name meaning of Nobotta's name, the first kanji of his name meaning to ascend while the first kanji of Orita's name means to descend. Interesting little detail there, considering what this fella goes through here lol.
So this one shot is set in a future Earth, possibly in the 2050s or so? Everyone's setting off into space, Tokyo's filled with smog, futuristic tech everywhere, local shops Nobotta always went to have all closed down, and we follow the descendants of the main Otoko Oidon cast. Meanwhile Orita's looking on at what's going on and is both confused and lonely, wondering "Am I gonna die?" like his 1970s ancestor would often say.
It kinda reminds me a little of the Spongebob episode, Gone, where Spongebob finds himself all alone in Bikini Bottom lol.