Galge no Sekai yo, Youkoso! - Vol. 1 Ch. 2 - The Intro's Promising

[MangaDex]

 

[Simpleton]

Rather than "old boy" for a previous student, the translation could have used alumni (the gender nutral) or alumna (the feminine form if we're guessing the former student was a female) which is are words used for a former student or graduate of a school, college, or university.

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Either way, thank you for your hard work.