Any connection to hopes peak in ndrv3?

Yep! Amami knew EVERYBODY from both SDR2 and DR1. Kodaka saying there was no connection was a great example of a lie.

They all exist in the same universe. It isn’t that far in the future.

So was Gonta killing Miu an accident? since his avatar did bugged out?

Shirogane caused the bug. She laid a trap to make Kaede “accidentally” kill Amami, as she KNEW his talent (SHSL Survivor) would lead him to yet another survival unless he did something about it.

Gonta’s avatar was bugged by Shirogane to kill Miu.

Wait, is Rantaro connected with someone we met in DR1/2/3?

Everybody. He knew everyone. How he did this I’m still figuring out…

So since Amami is the only character who knows the previous cast.. does this mean Junko's not actually the reason for the killing game? Since it's Tsumugi who's the mastermind?

Here’s the explaination.

V3 Universe is a rebooted universe that has nothing to do with the HPA Universe.  There were still two killing games for DR1 and DR2 casts, the survivors are as follows:Makoto Naegi, Mondo Oowada, Hifumi Yamada, Chihiro Fujisaki, Sayaka Maizono, Kyouko Kirigiri, Touko Fukawa (Genocider Syo), Junko Enoshima (It is unknown if she is evil in this universe or was the mastermind of her killing game.)Hajime Hinata, Teruteru Hanamura, Akane Owari, Ibuki Mioda, Chiaki Nanami, Hiyoko Saionji, Sonia Nevermind, and Mahiru Koizumi 

The rest of the DR1/DR2 casts are assumed either dead or part of a new terrorist group similar to ultimate despair lead by Mukuro Ikusaba. It’s probably the former though.

Due to this, AE’s events are different with Komaru dying and Yuta living. DR3 doesn’t seem to happen at all in this universe.The V3 kids fled to space due to an event that causes the world to go into a catastrophic tragedy and their plan was to stay up there until things were safe. Shirogane Tsumugi, however, erases everyone’s memories and puts them all through a killing game.

I'm so angry for shirogane. I love her. She'll probably die at the final trial? Is the mastermind the REAL shirogane? I don't want she die ;-;

The mastermind is the Shirogane that’s confused about the trials in the demo, the one who loves black-haired red-eyed characters, the one who loved making costumes for others, the one who was passionate and hopeful, the one nobody really looked twice at.