Now what if, hypothetically speaking, asking for a friend type stuff... What if the main character is so lazy that it is his first time seeing the world outside his, home, and has no connections with any other characters?
It would be very difficult to write in the style of In Medias Res for a wallflower main character... Unless they had attachments to the outside world or other characters before the story began.
You see sheltered/lazy main characters are very difficult for you to write In Medias Res. The way I see it the way you are laying out your story it seems more a Blank Slate style beginning rather than In Medias Res.
Whilst your secondary and tertiary main characters might have progressed further into the plot line your primary/central main character is the most important when it comes to the world building.
And from the way you are describing it your main character it would suit your story better to write in Blank Slate style rather than In Medias Res.
However if you do wish to pursue In Medias Res I would recommend doing one of the following:
1. The main character has a double life and the absence of connections is actually false.
2. The main character interacts with the core of the story is very little intentionally, and something in the past caused them to spark of this shut-in behavior.
3. The connections with the core of the story is accidental and has happened before, and the main character just has very loose connections to the world around them through the core of the story despite not wanting to be bothered.
And I would like to end on a note for you and
@TheMonotonePuppet:
I understand your cynicism of people that pretend to be willfully ignorant, and you defended In Medias Res well and I commend you for that.
However sometimes we have to realize that intention is lost through the Internet and some people actually wish to learn.
I understand where both you might be upset or confused with each, and I hope we have undone those misunderstandings.