It's supposed to be a surprise but sad panda doesn't allow for spoiler tags so... (´・ω・｀)

Raw

She needs to sit down and try a new tactic, like seducing him as a sister. After all that time, he's gotta have instinctual responses to her.

Base +6, Sanillam +13, soul saber +6, TheOneWhoScans +6, The14thNoah +11, Nobody_Know +7, Imsolo +6, AnEvilByte +6, 58569 +10, ScrawnyJohny +6, DerpiusDerp +7, Orengestar +7, sable1 +23, and 14 more...

That ending had me dying.

Base +6, Silver206 +7, Sanillam +13, soul saber +6, bunnygunny +8, Nobody_Know +7, Imsolo +6, Acerola +16, umumuchan +1, 58569 +10, DerpiusDerp +7, knucklesluigi +7, Dooderz +8, and 5 more...

@Mizaz - and a brain tumor.

Base +6, akseyd +6, The14thNoah +11, EllincedeT +10, Metatron0 +6

Lmfao this was fun.

Base +6, 58569 +10, Hugh Jarse +6, butt1234123412341234 +6

I think we can reasonably call her a yandere.

Base +7, The14thNoah +11, hjerry +6, Imsolo +6, faggotop +6, AnEvilByte +6, PinguPrin +7, 58569 +10, DoomTurkey +15, DerpiusDerp +7, coes159 +7, knucklesluigi +7, Hugh Jarse +6, and 9 more...

want to give this a male:ryona tag?

Base +5

Base +7, coes159 +7

Imouto-chan uses "Hammer Time" to induce Amnesia on Kazu-oniichan (I seem to recall there was an anime series which had a similar plot element).

"Well Isn't That Cute? ..... BUT IT'S WRONG!"

Base +7, The14thNoah +11, AnEvilByte +6, PinguPrin +7, Lin84210 +11, Spooky Ghost Butts +7, bigscuba +6, Fofotron +6

B-but wait, I mean, can't you just...

...I...

...bruh.

Base +6, Orengestar +7, Einaol +18, Spooky Ghost Butts +7

Just how long has she been doing this for.

Base +6, TrueRune +6, Hugh Jarse +6

Bonk, nii-chan is now my property

Base +23, Imsolo +6, sonnytag123 +10, 58569 +10, DoomTurkey +15, DerpiusDerp +7, knucklesluigi +7, Hugh Jarse +6, johj333 +6, EllincedeT +10, TheBrojangles +6, as102 +11, Spooky Ghost Butts +7, and 6 more...

Dude will eventually end up as a vegetable due to the daily brain injuries he receives, but I doubt she'll care as long as his dick gets hard.

Base +6, 58569 +10, Orengestar +7, Hugh Jarse +6, IMNC -6, EllincedeT +10, Dooderz -8, Spooky Ghost Butts +7, Fofotron +6

At this rate he’ll permanently regress to a baby state mentally...
Not that type of baby play you would normally want..

Base +31, AnEvilByte +6, knucklesluigi +7, Dooderz -8

And so the cycle begins anew.

Base +9, Hugh Jarse +6, EllincedeT +10, Fofotron +6

Wait...you were supposed to bonk the horny not get bonked by the horny

Base +7, AnEvilByte +6

This is like a Diavolo doujin adaptation:
Bonk #75729: Imouto takes me to the arcade where we had sex;
Bonk #75730: Imouto takes a shower with me;
Etc.

Base +6, Hugh Jarse +6

Wow. It was so short, but I'm sure I'll never forget that end. Good stuff.

Base +5, Hugh Jarse +6

Translations for [Yorisuke] Lo-Fi Cycle (Bishoujo Kakumei KIWAME Road Vol. 6)
Japanese RAW: https://e-hentai.org/s/8760e5405e/573296-146

Chinese: https://e-hentai.org/g/1666987/cbe8803ebb/
English: https://e-hentai.org/g/1664250/653f105e51/ (you are HERE)
Thai: https://e-hentai.org/g/1702979/48170aed93/

Base +18

Sooner or later, all those memory wipes will cause him to regress so far that he'll stop responding to any verbal stimuli altogether.

Base +9

This doesn’t really feel like yandere

Base +7