Bruh it's not that cut and dry, even the term NTR has 3 different meanings like netorare (being cucked), netorase (sharing) and netori (cucking others). So yeah sharing is technically a form of NTR, but cheating without the perspective of the one being cheated on isn't NTR.cheating in any form, even if you're sharing your girl by default is NTR, sharing a partner with someone is a type of cuckoldry, sorry you need to use mental gymnastics as a form of a defence mechanism when the suggestion of you might being into cuckoldry is involved.