Taishi Gotanda/Relationships

Aqua Hoshino
Gotanda has known Aqua since he was but a child -- back when Ai Hoshino partook in an acting drama. Ruby and Aqua are under the guise of being Miyako Saitou's children, as they couldn't let out the outrageous news that they were Ai's. Gotanda was initially quite cold to the child Aqua, warning him of consequences if he misbehaved. Gotanda was surprised when Aqua could properly converse with him. A feat that not even child prodigies possessed in his words. Aqua stated that Youtube was the excuse; Gotanda outright believed such a claim and said that Aqua is quite the outlier compared to other child actors. The two conversed as Ai was recording her takes. Gotanda told Aqua of the various things it'd take to survive within the entertainment industry and even asked him if he could offer Aqua a job. These series of events would mark the start of their bond.

It is unclear when but possibly as early as during the filming of That Was the Start‎‎, Gotanda has deduced that Aqua is Ai's child. Given that Aqua had no one other than his mother to look towards, he saw Taishi Gotanda as a paternal figure. Aqua would come to him for advice, and he reciprocated it with help. Their bond grew to the point where Gotanda showed genuine care whenever Aqua is distressed from re-living his bad memories. He also seemingly has no qualm with directing 15-year-lie, a movie that is part of Aqua's revenge plot.

Kana Arima
When Kana was still a child, Taishi casted her alongside Ai and Aqua in one of his movies. He didn't have very high opinions of her due to her bad attitude at the time. When they reunite years later, he commented that she still doesn't respect adults. Up until Aqua starts dating Akane, he imagine Kana would become Aqua's girlfriend. Later, they would work together again on the set of 15-year-lie.