Scanned and commissioned by me
Edited by Vilis from www.hennojin.com/scanslation/
Original translation by SaHa

I see enough new versions scanned or de-censored or re-translated or whatever, that I can't really make heads or tails of the plot anymore.

Does anyone have a breakdown of the course of events throughout the series? Like a Sparknotes or a Tropes page or something?

Base +6, Lostalgia +8, D. Hart +7, 151132 +7, Nack +7

Sure why not.
So here is the deal from what I can gather.
These aliens come to earth and infect people attempting to perfect them by turning them into angels. "Angels" can regenerate it seems, turn others into angels and have strong combat abilities also can possess others minds. The government gets wind of this and tries to use it to create immortality of sorts and the whole thing ends in a shoots out situation where a MC "dies?"

Fast foward years later to part 2 where we deal with the child of the aftermath of part 1 sort of dealing with the mess from before I guess.

Base +6, 151132 +7, Fills +6, Nack +7, tobeunforgiven2 +21

I'll see if I can fill in any missing details.

As mentioned one of the MC's (originally male) becomes being code named an "Angel" because aliens. As an angel s/he becomes more and more female gains the ability to control anyone who comes in contact with her body fluids and turn them into either an Angel or slave/drone. The created angels also can control people through their body fluids but can only make Drones. Hiding among the humans, she creates one special angel from her "prior to becoming an angel" crush (originally female). Through reluctant the crush eventually loses out to the perverseness and ultimately becomes her husband and impregnates her (the crush impregnates the original MC) and even gains the ability to turn others into angels as well (originally only MC could do that).

Meanwhile an organization/government (never really clear to me which) is monitoring the angels and interferes with them every now and then even kidnapping one or two for samples. I think that one high ranking member wants to be reincarnated as an angel and upon learning the MC is pregnant plans to reincarnate as her child. Stuff happens, big climatic finale, plans get messed up and in a shootout the Crush is shot with a lethal bullet (Iodine is basically acid to Angels, everything else they can basically regenerate).End Part 1

Part 2 take place a few years later, the child is born and grew up relatively normal but some time between parts 1 and 2 she goes on a rampage and rapes some girl. The girl is approached by one of the angels who secretly helps her and she gains angel like powers (due to being raped by the child) somehow involving snails that are nearby. Meanwhile the child has no memory of any of this and her powers are usually kept in check by the MC/mother. More stuff happens involving the girl seeking revenge and the Child awakens the sleeping being inside of her who at first the mc is afraid is going to be the high ranking member from before but instead turns out to be the crush/husband. Continuing the revenge the girl goes on a camping trip with the child which descends into debauchery (mc is unaware of the other girl and the angel who is helping her at the time) and that's basically where we are.

Base +6, raifox +7, Zero9x +7, BZFS +6, Fills +6, Nack +7, Patchouli42 +6, rabidalien +7, shingofan +8, tobeunforgiven2 +21