Parasocial relationships refer to one-sided relationships in which a person develops a strong sense of connection, intimacy, or familiarity with someone they don’t know, most often celebrities or media personalities. These relationships exist only in the mind of the individual, who experiences a bond despite the lack of reciprocity.
Forming parasocial relationships is fine.
Fapping (masturbating) to nsfw content is fine (unless it is illegal or unethical).
But forming a parasocial relationship with someone you fap to feels like cheating if you are in a relationship and a poor substitute for a relationship if you are single.
This is an extremely normal opinion, have you been fraternizing with people who think otherwise? Parasocial relationships are commonly mocked