Here, the real one is marvin's story, I think mp was inspired to make his background in insipid stories, reluctantly, for someone of such an age as marvin, for example; removing the one of being a vain old man, or sex offender, he could have Obsessive-Compulsive Disorder, Narcissistic, Antisocial Behavior, that is to say that he appears to be a nice person when he is not, that would be a key piece for a narrative for Marvin, besides increasing him from a few years, about 70 years would be the right one.
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That certainly is another way to make a Marvin
How I see Marvin currently as a hollow failed man lacking empathy.
Now, there are a few people who age well and others who don't... Marvin is in the latter category. It doesn't so much have to be about looks, but it helps. I suspect Marvin is the same person as when he was in his prime (shallow). But there still is plenty of room in the story to evolve Marvin based on his current characteristics, behavior patterns, and character build and still keep Marvin, Marvin. There is one trait that bests describe Marvin is he is treacherous. So however you evolve his character, Marvin will in the end serve his own ends.
All that means Marvin could ally with Anna, show compassion, and play into whatever Anna wants (like teasing him) or do her favors so long as he figures he'll get something out of it. He'll be loyal only as far as he sees he's getting something out of it. The other main trait that describes Marvin is he's not very tactical or strategic nor has his life experiences taught him how to read people. Otherwise, he should pick up on Anna's clues and exploit them.
For now, Marvin has allied with Kendra because that gets him what he wants... but Marvin needs to realize he has nothing to really offer Anna and should realize Kendra has no real way to deliver what he wants. I doubt Kendra even takes serious that Marvin would have a chance with Anna. At least he ought to realize he's outclassed with a woman like Anna because likely Marvin has throughout his life been shot down by such women. So the best plan Marvin can do is play Kendra against Anna because he's onto Kendra and would know Anna is being blindsided by Kendra... and play Anna against Kendra to score points with Anna {doesn't mean Marvin would tell Anna what Kendra is up to but wait for openings and opportunities that wins points with Anna at the expense of Kendra's Plans).
Thing to remember is I doubt Marvin wants to share Anna with anyone in the office and wants just a little more than a cheap thrill--he can find and pay for that on the streets.
All that is left is for the story to unfold where Anna becomes her own worst enemy when it comes to Marvin-- that quirky little thing that allows herself to want to tease Marvin and get a cheap thrill out of goading Marvin
