Alright guys, this might make some of you cry.
Who is he?
Basil is one of the main protagonists of the psychological horror RPG, Omori. He was once a happy, social young boy, but Mari's death and his role covering it up have caused him immense trauma, and he's lost the friends he used to have. His fate is in the hands of his former best friend, Sunny, who can either save his life or let him suffer a horrible fate through choices you make in the game.
What do people like about him?
He is an incredibly tragic, complex character, and his fans think he's a very well-written character. He suffered through nearly as much trauma as Sunny, due to his role in Mari's death being framed as a suicide.
He is essential to the plot, being arguably the 2nd most influential character in the game behind Sunny/Omori himself.
Fans consider his design to be cute, particularly his Headspace version.
Has a very complex and deep-rooted relationship with Sunny, being his best friend who he'd do anything for. One of the most popular ships in the franchise is Basil x Sunny, and some even consider the ship to be canonical.
In the end, his photo album and all the memories within it are one of the main reasons why Sunny is able to move on from Mari's death.
What do people dislike about him?
Detractors criticize his role in staging Mari's death as a suicide. When Mari was killed by Sunny who pushed her down the stairs, a panicked Basil came up with the idea to hang Mari's corpse to frame it as a suicide. His detractors think that this was a dumb idea from the start, as he could've at least tried to call for an ambulance even if she was dead, and covering it up ended up arguably only hurt the friend-group more than if he was just honest about it.