For real. There are two characters that spell Ichika in Japanese. They happen to be the exact same characters, just backwards for Naruse's first name Keiichi. So I'm guessing that's where the confusion came from when Daiki is referring to Ichika and says Keiichi instead.
Okay, saw the kanji if katakana is not used 成瀬 (Naruse)... then 壱佳 (Ichika) and 圭壱(Keiichi), you wouldn't notice easily but when you look closely. The kanji position is diff. and Keiichi has no 亻component in 圭 . Idky they keep the Keiichi, first name basis is a sign of disrespect unless you're very close and permissible. Otlz, this makes Daiki's character look bad.
And a little bit funny that Daiki is on first name basis while Asumi still in last name (T∇T)
(@Д@;;;) very confuse whether the translator intentionally done this, so we will not be confused about who Daiki is referring to. Since there are two Naruse: Keiichi (father) & Ichika (son). Or just rush job w/o proofread and QC.