>>16901017To clarify your statement, it relates to seniority. You don't call someone sempai unless you're both part of the same organization, like attending the same school or working for the same company. It's like an expectation for the experienced to mentor the noobs (that you explicitly remind them of every single time you talk to them). It's not purely age-based; someone younger than you is your sempai if they joined sooner.
>>16897952Younger than that doesn't really have the strength of body to do serious damage. Also, tweens are more likely to have unsupervised access to sharp things than younger kids.