From my understanding probably to addressing in a respectful mannerI had a quick question, I know onee san and onii san are not only for siblings but also to address someone older than you but for some reason they both address each other as such. Is this a joke with him addressing her as older because she's tall and her addressing him as such because he seems more mature?
It's fairly standard polite-formal address for someone who you aren't calling by name and who is closer in vibe to a young man/woman than an older man/woman (unwillingness to accept being addressed as Oji-san/Oba-san instead of Onii-san/Onee-san being a trope mostly played for comedy a la Kaiju No.8's Hibino Kafka insisting that he is still young at 32 years old or the Western "call me Miss, not Ma'am" equivalent).I had a quick question, I know onee san and onii san are not only for siblings but also to address someone older than you but for some reason they both address each other as such. Is this a joke with him addressing her as older because she's tall and her addressing him as such because he seems more mature?
It's just emphasizing how awkward they are. They haven't figured out exactly what their relationship is, nor have they exchanged names and even if they had they'd be worried about offending the other (whether to use first name or surname, and which honorific). The only concrete relationship they have is them being deliver driver and client. So they're sticking with a "safe" (polite, impersonal) manner of address.I had a quick question, I know onee san and onii san are not only for siblings but also to address someone older than you but for some reason they both address each other as such. Is this a joke with him addressing her as older because she's tall and her addressing him as such because he seems more mature?