Naotsugu is two years older than Shiroe, and they first met four years before the Catastrophe when Shiroe was already a veteran player. They are close friends and have even met offline several times. Due to his work schedule, Naotsugu has been absent from Elder Tale for two years and had the luck of being caught up in the mess on the very day he returned to the game.
In Shiroe and Naotsugu's first offline meeting, Naotsugu's uneducated remark about Shiroe's tea led to a thirty-minute-long lecture on Shiroe's part about the difference between black and oolong tea. That then led to a discussion about Taiwanese politics, the European Union, and the economics of tea. Ever since then, the two have been best friends.
Naotsugu follows Shiroe's leadership without question (aside a few times shortly after the Catastrophe) and trusts Shiroe's intelligence to get them out of any situation.
Originally, Naotsugu thought Akatsuki was male due to her male avatar until she spoke and used a potion to change to her real gender. They almost immediately got off to a bad start and have had a shaky, if not violent relationship ever since.
Naotsugu constantly mocks Akatsuki for her height and apparent youth and she constantly disrespects him and hurts him before he can say anything perverted and then asking Shiroe if she can hurt him after she's already done it, much to Naotsugu's aggravation.
They barely tolerate each other and there are rare instances they get along.
Naotsugu has a very dynamic and uncomfortable relationship with Tetora, due to her flamboyant, extravagant, and self-absorbed behavior, and she constantly flirts with him in a teasing manner, much to his discomfort.
Naotsugu doesn't know it but Tetora is actually male in real life.
Naotsugu first met Maryelle after the Catastrophe and despite her overly-huggy personality, they hit it off well and they have sparked a mutual attraction.
Naotsugu and Shoryu get along well but Shoryu is crestfallen because of his crush on Maryelle but he suspects (correctly) that she has feelings for Naotsugu.