Shigekuni Nandaba is Naota's grandfather. He owns the family bakery and coaches the local baseball team, the "Mabase Martians." He has a grudge against Mamimi because he didn't approve of her relationship with Tasuku. Shigekuni values baseball more than anything else in the world — he is disappointed in his own son and younger grandson because they are lousy baseball players. He does not defend Naota as the other players mock him, because he holds too much pride for Tasuku. He enjoys taking advantage of Canti as much as Kamon does. He has an affinity for pornography: in the first episode, he mistakes "furi kuri" with "kuri kuri," a sound effect that is often used in hentai during any twisting motion, often involving the breasts or nipples.
Shigekuni is a stern, reserved man by most accounts. Director Yoshiyuki Sadamoto describes him as having a "strong personality" in his Newtype USA section. He is harshest on his family because they do not meet his standards. Whether it is Tasuku's relationships or Naota's baseball skill, Shigekuni does not let up. However, he does seem to judge Naota and Kamon harder because Tasuku is so good at baseball, something he takes pride in. His serious nature is only lost when Haruko is around, bringing out a perverted and "immature" one seemingly held by all FLCL adults. He, along with Kamon, have a tendency to change the subject to things of a sexual nature when their maid is around, often misconstruing her words. If not for his age, he likely would pine after her relentlessly like Kamon does.
Shigekuni is a weathered, wrinkled man who doesn't try to hide his age. He has a large bald spot going from the top to the front of his head, leaving only short, scruffy sides. His eyebrows are grey, along with his hair, and have a large, angular arch. Having an incredibly short nose and large ears, he somewhat resembles a monkey and usually bears a tired, disapproving look. He almost always wears some pieces of a baseball uniform, sometimes ranging from just the jacket to the full outfit, with a long-sleeved shirt and sweatpants if necessary.