Remove where I usually order a large latte and muffin
This is a complex sentence it includes a subordinate clause (one that CANNOT stand by itself), and a dependent clause. You can tell this because if I were to walk into a room and say, "When K and C read the same foldable....", you would be waiting to hear the rest, wouldn't you? A compound sentence has two independent clauses joined by a comma and a coordinating conjunction (but, and, for, nor, or, so, yet). A simple sentence is just an independent clause.
The mood (or tone) of the prologue is considered as sombre, dark, macabre... since from the start we're being told that this story is going to be a story of love, death and loss.
B. That his body dissolves into the air and water.