Counterattack System appeared when I'm already At The Mahayana Realm - Chapter 664 - 663: The Trembling Immortal Realm

My older brother, who was my only family member, lost his memory. “I have a sibling? Are you kidding me?” He was a fool who cared for me ever since he brought me from the temple… “I can’t even take care of myself, so what is this…” I left the family because I didn’t want to be a burden to my older brother, who had no memory, and was helpless in the tragedy that followed. So I turned back time. That too, to the point when my brother lost his memory. “I don’t have anything in my head, so I don’t know what to do next. What if I have a kid with me?” We must not repeat the tragedy of the past life. So I grimly said, “That’s right. I don’t have anything on my brother’s head right now.” “…What, what?” I chuckled and took out a document I had prepared. The contents of the document, written in crooked, large letters, were simple. [I transfer all the property in my name to my younger sister.] While my gaping older brother was checking the documents, I took out his seal from his drawer and smeared it with ink. Then I put it in his hand and said with a very sad expression. “So stamp it. Now.” I will protect you in this life.

Du Fei was reborn, and in this difficult era of extreme shortage of supplies, he started his wonderful life of opening and hanging…

- Description from novelbuddy

So here's the pitch: I got reincarnated with Mangekyo Sharingan.Sounds overpowered, right? Instant win button?Except I can barely keep it active for thirty seconds without feeling like my brain's being microwaved. My chakra reserves are pathetic. My combat experience is zero. And the system that gave me these powers took one look at my situation and said “good luck” before fucking off into hibernation.Oh, and the Hero Killer—the guy who murders heroes for not being “worthy”—just decided my mom wasn't good enough. She'll never walk again.I know when he'll strike next. I know where. I've got exactly four weeks to train.Four weeks to go from “can't throw a punch without tripping” to “can survive a fight with a serial killer.”The smart move? Stay out of it. Let the pro heroes handle it.But I'm fifteen, angry, and apparently making life decisions with the wisdom of a shounen protagonist.At least I'm in General Studies. Low expectations.What does being a hero have to do with revenge anyway?

Almond Crowshade was the last surviving human in a dying world whose people failed to conquer the Grand Abyss Labyrinth’s 30th floor in time. The world was getting destroyed, and Almond was the last one challenging the 30th Floor multiple times despite the imminent destruction of the planet. He ultimately defeated the Floor Boss on his dying breath by achieving a true awakening, acquiring an X-rank Trait that signified limitless potential. Alas, he won but there was no home or future for what he fought. But a mysterious figure arrived there, feeling pity and amusement. “This is too precious and fun of a toy to let it rot here. You shall reincarnate and climb up to make things interesting.” [Transfer to another world commencing…] [Your memories will be sealed, and you will reincarnate in another world that has welcomed Grimworld’s tutorial like this one. Clearing each floor of the Grand Abyss Labyrinth will unlock a portion of your memories, until the 10th Floor upon which you will gain your full memories.] ‘I’m giving you a second chance. This time, you must clear the Grimworld’s tutorial and step onto the big game to make things instresting and entertaining.’ [Good luck.]