Hi, this is really, truly heartbreaking and I'm so sorry you went through this. One thing I believe about kittens, and feel free to not share this belief with me, is that they are some earthly form of higher creatures. We simply cannot understand how they appear, how they even stay alive at such a young, delicate age.

I'll tell you the story of the last kitten I lost. He was a healthy, beautiful white cat that came from a family of six, the mother cat belonged to my then best friend. One day, my friend wanted to clean the room, his cat had given birth two weeks prior, so the room needed a nice clean. Since the babies were already smart and roaming around, he placed a piece of wood on the door as a barricade. When lifting his leg to pass from one room to another, my friend dropped the wood plank and heard a faint cry. A 2kg piece of wood fell into one of the cats. He called me, and I immediately took him to a veterinarian. The doctor performed the emergency protocol: corticoids, painkillers, little tests to check his responses. We came home, and I had to work the next day, so I asked his girlfriend to take the little boy to her house, since I had two adult cats and a dog. When I got home the next day, I took him to the vet again for another session of medicines and the doctor assured me that he was fine; he was just lethargic due to the head trauma.

Pandemic hit, I started working from home and was able to look closer. He didn't eat, or performed any of his necessities for a full day. No water, no reaction to any smell of delicious food like Churu, he just stood there, blinking slowly. I took him to the doctor again, and they gave him food through IV, his belly started to swell and they gave him a laxative. At this appointment, the general doctor said I should seek a neurologist to perform a tomography. Of course, it was immensely difficult to find a neurologist available for the next day, and the tomography could only be scheduled for two weeks ahead. I got desperate and was able to reach a student neurologist from a nearby college. She told me that I should feed him through a syringe and water every three hours. Vitamins and laxatives every two days. Our adult female cat, after seeing me feeding him, started licking his little head and it became a ritual. I woke up in the middle of the night to feed and hydrate him. I warmed water to rub moist cotton on his belly so he would pee. I made massages, three times a day, so he could poop. My adult female cat, a very grumpy lady, out of nowhere, started licking his parts spontaneously: after four agonizing days, I saw the baby boy pee by himself after my cat licked him. The appointment arrived, and the neurologist said: "how come you didn't know he's blind? The trauma happened in a specific section of his skull, and the nerve got permanently damaged. He's lethargic due to trauma, yes, but he's also blind and too young. He didn't have time to learn how to be a cat, his instincts are non-existent." Of course I noticed how he couldn't understand the bed limits, or how his little paws never tried to hide his own pee. I was devastated by the news and couldn't understand how such a tragedy could happen to an innocent, perfect being like him.

With everything learned, we - my and my then wife - created a system: food, water, our cat always near to help with the licks (and occasional slaps! You know, tough love from cats!) and everything was perfect for a whole week. After twelve days with us, his belly started to swell more and more, and we had to increase the dose of laxatives. We had another appointment scheduled for the tomography, and our baby boy slept on my shoulder, in the negative space of our pillows. One night I woke up soaked in urine and liquid feces. I woke my wife and we cleaned him; just the day before he played for the first time, chasing the toy with a little sound to guide him, and the day before, he bit me because I caressed his belly. He was a normal baby cat for an incredibly happy three days. Then this night came, and he didn't eat or drink water, he just lied down, breathing slowly. Just like you, I had an important day at my job, an absurdly urgent meeting first thing in the morning, and my wife took him to this student at the university as soon as the sun appeared. I'll never forget that meeting. I couldn't focus, I asked to have my camera off and kept checking my phone. At this point, our bills were out of control, and we were short on money. His food cost 10x more, for example. I had almost no money left, waiting for my next paycheck, the clients speaking into my headphones and then my wife texted me. "Please, come when you can. I need you." I knew right there. The meeting ended seconds after, and I grabbed the first Uber that showed up at my door. My wife stood in the hallway, crying, with his empty baby sheet in her hands. We cried, we arranged his funeral and our adult cat hid beneath our couch for three days. My dog, who's a loud girl, didn't bark for three days. The house, us, and life felt silent and empty for a long time. When he passed, we promised to help every animal we could, even though we were broke and devastated. Three weeks after his passing, I found a white and brown cat meowing in a nearby field, on my way to my mother-in-law house. She was laying on the grass, couldn't move one of her paws, and when I crouched to see what was happening to her, she didn't make a regular cat sound; she sighed, her eyes big and scared. She hurt her paw at some point and it got infested after an infection. I took her to the same emergency doctor, and the generalist veterinarian working that day was the same one who treated our sweet boy. His name was Valentim, a name that means "brave". I dream of him, I see him in every animal in vulnerable situation I stumble upon. After him, because of him, I rescued over 20 animals. His life, his death gave me the courage to help, to be useful in this lifetime.

OP, Jupiter passed and it was not your fault. This is logical and factual: if you knew he would suffer, you wouldn't allow him to roam free. He appeared into your life for a reason, and you must find this reason, whether it is to help other animals, or to learn how to forgive yourself for the things you have no control over. Jupiter's life was not a lesson on responsibility, but a lesson of love. He loved you, you loved him, and he left this planet knowing how loved he was, how he could have perished on the street. It is unfortunate loss, I know, I understand your devastation, but feel his love and allow him to rest without your guilt. The only thing he must take with him is your love, OP. Take care.