Mu-kun keeps calling him sensei, but he seems to always be on a business trip. I can't imagine a professor or teacher would constantly be on a business trip.
From getting back pain to successfully catching her without falling from the stairs, our Mu-kun right here must be training for these kinds of days in the future.
@HOOfan_1 'sensei' doesn't necessarily mean 'teacher'. It's used as professional courtesy, usually to someone who has an expertise. Mangaka, writers, doctors, for instance, also get called 'sensei'.
Japan's school system actually mandates teachers teach at schools in different areas on rotations. It's egalitarian, but can be a real pain when you're sent to teach in a rural area well away from your home. I'm not sure if this is his case, but another manga "Yandere Kanojo" has a similar father-teacher situation.
"La Pucelle" french word for a virgin woman.... they both know that they aren't anymore haha
Anyway Atta-Mu-kun xD
And business trip is not only in other countries but can also be made in the country.... So my guess is that the father is a lecturer and was dispatched for some work or he himself asked to work on his subject... (like archeologist or historian... Historian being my second guess)