You might find that you are a discovery writer. My characters have the frustrating tendency of doing things and meeting people. I keep thinking ‘great, another character - this is getting crowded’, but it is. I start with a name and that informs me of the heart of who this person is. Do they know my MC? If so, how and how long? Will they help or hinder?
In one case, I had one situation where a character asked another if Morgan, who was nearby, should be sent. I asked myself ‘who is this?’ and came up with a rather intriguing character. I discovered that she was from Missouri, had strong self esteem and a quick wit. She never fails at her task (professional kidnapper) and finds that the more that she uses the force of her personality, the greater her success regardless of the training of her targets. She started to grow as I put her in new situations and she revealed aspects of herself.
If it were me, I would have Mike meet someone, might not be the first person he encounters, but someone who adds what is missing. Maybe he meets a sardonic middle aged man named Everett (got teased a lot by some, but grew more determined and learned the importance of self-reliance. Doesn’t come from money but his parents thought a name like that would improve his chances of success in business.) Create this character, see him in your mind and how he interacts with Mike.
Does Mike like him? Respect him? Does Mike wish he had turned right instead of left if only to avoid running into Everett? Do they have a long-standing relationship or is this some walk on character who exists in part because the world has people in it and the streets are not empty.
Step inside Everett for a moment - who is he? What does he want? If Mike needs to meet Abby to get to location X, perhaps he knows about location Y and is going there. He might invite Mike to join him, creating a bit of an obstacle and a slight red herring.
Adding obstacles and creating characters to overcome them certainly works. You can end up with an interesting group of characters, some of which might be more interesting than your protagonist. The Belgariad did this, an ensemble cast with some very engaging secondary protagonists - each had a role to play.
If there is a compelling reason for Mike to be alone, wandering and eventually finding his way to Abby, that could give you a good opportunity to learn about him, but it could come across as an info dump, so be careful. Having only one other character certainly makes it obvious that here is a person of importance - only two people, one cannot be just fluff.
Consider adding a couple of characters as foils, but give them lives and characters of their own. Someone might be willing to help Mike, knowing that Abby is likely to know what Mike does not. Said character might tag along out of curiosity and just be there for the occasional renark. Can’t let Mike’s status as MC go to his head - some ego trimming might be in order.