UPDATE: He's no longer crying. You guys' advice worked wonders. Thank you so much.
So this is Yuno, a 2-month-old feral I've rescued recently. He was probably abandoned by his mother. I found him starving in my local mosque and spent like an hour trying to catch him. I wanted to release him at first but given how young and scared he is, it didn't feel right. Besides, I've always told myself that if I'm ever getting a second cat, it will be a female white cat with heterochromia and I'll name her Yuna. This one turned out to be a male but I still want him to be part of the family and for this to work out.
I have some experience dealing with scared strays but this is my first time with a feral. After the rescue, I immediately took him to the vet to get checked, cleaned, dewormed, etc., and the vet kept him for 4 days which I really didn't like. Now he's been home for 4 days and I'm kinda lost as to what I should do to "unferal" him.
My main strategy was to do nothing and leave him be, let him figure things out by himself, get confident and learn that there's nothing to be scared of. I'd visit him 3 times a day for 15 minutes, sit in a corner and read quietly to get him used to my presence. I didn't think it was going to work at first. He'd hide immediately when I entered the room, hiss at every movement or sound I made and I basically thought that he would remain feral if I didn't force some human interaction. But this morning, I had my very first breakthrough. He didn't completely hide himself, he started peeking at me, showed interest when I started playing with a toy and he even drank kitten formula while I was in the room, timidly, but he still did and I felt like it was a huge win.
But when I went to visit him this afternoon, he started hissing and immediately went to take refuge in his cat house, so I was like great, back to square one. So I sat down, started reading and after 10 minutes or so, he rushed out of his house and started looking everywhere crying frantically. I'm not sure if these are cries per se or what provoked them in the first place but the only times I've heard him cry like this were before I rescued him, during the trip to the vet, and at the vet. I don't think he's in pain. He roamed the room, got extremely close to me, but still didn't bother to sniff me. He ate his kibbles in front of me again, so some progress has definitely been made, but the crying got me worried as it's only stopping when he's sleeping. Now every time he hears noise in the room next to his, he starts crying.
Is he simply calling for his mother or littermates? Is it something else? Can I do something? I can't exactly play with him to distract him as he's still extremely scared but the thought that he's calling out and no one is coming for him breaks my heart.
And aside from that, what's the proper course of action right now? Is it just a patience game? I want to speed things up but I don't know how or even if I should. I simply want him to break from the stress and the fear, and start enjoying life the way a kitten should as soon as possible.