Well, Reki Kawahara built the interaction of the characters so that everything revolves around the harem, but never crosses the border. In the novel, unlike Fujino's game, the characters generally understand everything. Asuna realizes that Kirito is too good at what he does, and "girls in distress" are constantly flocking to him like moths to a fire. In the novel "Alicization," Asuna, when she joined "Underworld," wonders how Kirito, even sitting in an armchair like a vegetable, is able to gather loyal friends around him, and especially girls who have been taking care of him for years.

Kirito also understands that the girls around him have feelings. And he always doubts in his mind whether this or that action will be considered treason.
Volume 6 - Chapter 9, before the final round of BoB. Kirito: "I really won’t dare to say this to a real person in the real world.
No, considering that I already have a girlfriend in Asuna, it’s unforgivable even in the virtual world. However, I dare to swear to god that this isn’t about trying to get a date in the VR world, but to fulfill my duty and mission, and also a necessary step to ensure Sinon’s own safety."
During BoB's time, Kirito had already realized that Sinon had feelings (just as Asuna knew it) and was worried that both girls would misunderstand his actions.
Plus, I've already written about the "There is But One Ultimate Way" dojin. Although it is considered uncanonical, however, it was written by Reki Kawahara himself and essentially describes a full-fledged harem with Asuna's participation. So whether to consider it canon or not is a matter of personal preference

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"Kirito awakes in a bed in Underworld and soon realizes that he's surrounded by Alice, Asuna, Leafa, Silica, Lisbeth, Sinon and Yui. After they wake up, they start talking and Kirito asks for answers about what's happening. In the conversation they reveal their uncertainty about the future, as Asuna and Lisbeth are about to graduate, and chances for meetings may become rare.
As such, they want to spend the last of their holidays together. All the girls confessed their love for Kirito

, and made an agreement to get married to Kirito in Underworld, unbound by real-world constraints.
As their holiday is ending in a few hours, Kirito agrees to quickly get married at the church in Centoria. The girls then revealed that they all are in the Soul Translator running at 10,000 times faster, and still have 5 years, 8 months to go."
As for the reverse NTR, Fujino implemented it in his own style. Liz wants to take Kirito, Suguha wants to own Kirito, Sinon also wants Kirito as a toy, apparently. Even Alice, for a hypnotized whore, spends too much time on Kirito. But Fujino did everything very clumsily and without zest. So I guess that's not what you wanted...