@takio She's the fl for sure,maybe thats why author haven't make a scene that they having a s*x with no string like this. Mc is very professional about his "job" so if yuna and him have a unexpected s*x the results might be like this,just s*x no feelings. Maybe author wants the best for the main characters. Like more into romantic love making,with pure love interest not as a job or one night stand. In that way it will be obvious that yuna is the fl here, because mc treats her with respect and gentleness unlike how he treats the other women's.