Tasuku Nandaba, 17 years old at the beginning of the series (his current age is unknown), is Naota's older brother who moved to America to play baseball. Mamimi believes that, since Tasuku saved her from the fire at their old elementary school, he likes her and it is continually suggested that Naota serves as a sort of stand-in for his brother (most explicitly by Mamimi's use of the same nickname for both). The actual depth of their initial relationship is unknown. In FLCLimax, she seems to have lost any hope in him, allowing the destruction of her mobile phone just seconds after looking at his number on the screen. In the first episode, Naota receives a postcard from Tasuku, revealing that he now has an American girlfriend that Naota decides not to reveal to Mamimi.
Although he never actually interacts directly with any of the characters in the series, he is very significant to the first season's plot. As the former star of the town’s baseball team, Naota idolizes him, but he is afraid of not living up to his brother's legacy, and, because of this, he never swings the bat when at the plate. Naota must learn to overcome this in order to save Mabase in future episodes. He is also the driving force for Mamimi's character development as a result of her attachment to him.
- There are examples of scenes in which Naota yells out "Tasuk--;" the Japanese audience, at first assuming that he will exclaim "Tasukete" (Help me!), may be surprised when he instead says "Tasuku," the name of his older brother.
- Naota says in the first episode that, for a moment, Haruko resembled Tasuku. This is likely because he takes notice of maturity quickly when assessing people.