This theory follows after the Good Ending of the RPG Horror Game known as OMORI.

The ends with the following scenes.

The following scene appears with Sunny entering the room where Basil is with the rest of his friends.
Which after Sunny says "I have to tell you something"

This applies that Sunny has finally told the Truth about what Sunny and Basil have done in the past and how they lied to their friends for 4 Years.

The Truth about what you may ask?

Well 4 years before the game starts Sunny had a argument with his sister Mari,Sunny threw his expensive violin down the stairs and broke it because he didn't want to play the violin anymore as it was taking so much of his time and never had any time for his friends.

Mari got angry and started yelling at him but Sunny tried to run away but Mari tried to stop him.

Sunny started struggling and in frustration pushed Mari down the stairs which killed her...

So is that it and what did basil have to do with this??

Well Basil saw everything and after Sunny laid Mari somewhere and tried waking her up....there was no response.

Mari was not breathing....at that moment Sunny started crying.

But then Basil had an idea about how they should fake a suicide on Mari to avoid being blamed.

Basil and Sunny then tied the ropes and everything and hung Mari.

And that's the truth is..Sunny & Basil have been living with this guilt for 4 Years and have been haunted by it.

So lets go to the part where Sunny tells the truth.

So after Sunny tells the truth would his friends forgive him and Basil?

Kel : Kel is a very positive person and he is a good friend to Sunny.
Chances are that he might forgive Sunny & Basil but there will probably be a small distance between their friendship

Hero : Hero is a kind and loving person and always admired Mari...after hearing the truth i doubt he might even say anything,Hero will probably just leave the room quiet and forget about Sunny and their friendship.

Aubrey : Aubrey is a person who is true to herself...Mari's Death was a lot for Aubrey as she changed and not in a good way...she started bullying Basil because Sunny marked all the photos of Mari in black in one of his old Photo Album but Basil took the blame so Sunny doesn't get in trouble....that just goes to show that Aubrey was angry on how he could do such a thing but Aubrey is still a good person but after hearing the truth...lets just say that she might slap Sunny or something and then start yelling on "HOW COULD YOU DO SUCH A THING?!?!" and stuff like "YOU LIED TO US FOR 4 YEARS!!??"...and then she would leave the room in disbelief..

After all that Sunny & Basil 's guilt would be off their chests but at the price of their Friends Pain.

Hero & Aubrey probably won't be seen with Sunny again but its time for Sunny & Basil to move on with their life after 4 Years.

(Aubrey might start turning around after some time but the same might not be said for Hero)