An angel will come to help Nanno take down Yuri and Junko in Season 3.
Since "The Judgement" has revealed Yuri and Junko to be the Big Bad Duumvirate of the series who are hell bent on ending humanity altogether, Nanno will need a lot of help in taking them down as she is completely powerless against them. Possibly an angel entity will come in to help her, as she and Nanno are best friends from the different sides. The angel's abilities are to save lives, protect and heal the innocents. It's later revealed that the angel has a dark past of her own where her boyfriend was murdered by Junko, which she finds out later. The angel accompanies Nanno to prevent the damage Yuri and Junko might do and protect those who may have done bad things, but aren't malicious as they may have sympathetic reasons behind it, but Yuri won't be that understanding and will still sign a death warrant for them because in her eyes, "any misdeeds are still evil misdeeds". Nanno and the angel will become very close and one of the only things Nanno will realise that might help her defeat the two villains is the Act of True Love she has for the angel and T.K., who himself will also return when the angel is tasked to protect him as he ends up on Yuri's hit list because of his past as a shoplifter. The angel will even manage to grow a spine, going from fearing Yuri and Junko to giving them "The Reason You Suck" Speech to them, telling them that they are even worse than the people Nanno takes down and they deserve to go to hell for it. The series will end with Nanno finally earning her happy ending after being put through so much sheer turmoil by Yuri and Junko and deciding to grow old with TK.
After all the hell and trauma Nanno was put through in the second-half of the series caused by Yuri and Junko torturing her, she will finally have enough and stand up to them and give them a Karmic Death to end their reign of terror. And based on her empathy towards moms in Season 2, she will finally decide to retire her immortality and start a new life with TK, running away to another country with new identities and have a family and grow old with him. Yuri and Junko will hijack the government where Yuri will become a tyrannical dictator and start a fascist regime where she commits mass executions or life imprisonment and torture against those citizens who broke the rules she created and turn Thailand into a dystopian country. Season 3 will be inspired by 1984 and V for Vendetta
The series will have a Bittersweet Ending for Nanno and her adoptive sister who is an angel entity where they finally defeat Yuri and Junko and end their reign of terror and deciding to give up their immortality and retire to live normal lives with their partners. However in order to achieve that, they're forced to lose memories of each other and never see each other again.
Yuri is a leader of The Syndicate where she orchestrates crimes and attacks around Thailand. Which was the reason why she wanted to kill and destroy Nanno to make sure she never knows the truth.
It's possible that based on the fact she is used to committing crimes and getting away with it because of her power and privilege and the fact she was revealed as the Big Bad of the series in "The Judgement", Yuri may be the mastermind leader of a crime syndicate and is using the powers she got from Nanno to restart and pick up from where she left off to continue causing chaos and destruction around the world. It could also imply that she faked her poor background to con Nanno into helping her when in reality she was rich all along.
