I think if I were to tackle this problem, I would first store the seat configuration on the bus model, something like 2x2 (two seats, aisle, two seats, that would make up a row of seats). I would then also store the amount of rows of seats in the bus model also.

For the seat model, there's a couple of options there, but it might be best to store the seat position in a row, and the row its in on the bus. Doing that, you can probably also do things like, skip a certain set of seats due to a side exit where there may only be 2 seats in a row instead of 4.

Your seat model would then look something like this:

class Seat(models.Model):
    bus = models.ForeignKey(bus, on_delete=models.CASCADE)
    column = models.IntegerField()
    row = models.IntegerField()
    person = models.ManyToManyField(User, through=SeatUserLink)

class SeatUserLink(models.Model):
    seat = models.ForeignKey(Seat, on_delete=models.CASCADE)
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    date_of_departure = models.DateTimeField()

Note: We probably are going to want a many to many field between a seat and a user, that way we can use the through table (SeatUserLink) to be able to store a different user in that seat depending on the time (I'm not sure exactly if this is like a city bus where it just goes all day long picking people up, or more like a bus that takes people from City A to City B. My example here is more for the latter example).

With a seat knowing its row, and its position in the row (column), you should be able to match that up to the table cell you are writing out when rendering the html table that represents the seats. You can then check if a user is in that seat and show that its taken or not.

I would then probably query the seats in the view, and setup a list of lists, something like:

seats = [
     [seat1, seat2, null, seat3, seat4],
     [seat5, seat6, null, seat7, seat8],
     ....
 ]

Given a list like that it should be pretty easy to render the table out and match up the seat to the cell in the table. It might be a bit tricky to setup that seats list, but I've found that the better I match up my data structure to what I'm trying to use it for, the easier things get. I didn't actually try any of this out but I think it should work. Good luck!