Tenshi's punchline, "上から来るぞ!気をつけろぉ!" ("Beware of what's coming from above" or "Incoming from above! Be careful!") is a quote from the opening video of Death Crimson, a game infamous for its low production values. The quote in question, like most other parts of the opening, seems weird and exceedingly out of place.
This particular line, aside from the hilariously bad voice acting, is weird because the main character (with his companions) are climbing up a set of stairs while he proclaims the enemy is coming from above. It doesn't help that the opening video in it's entirety is so obscure.
You'll come across this phrase from time to time in places like Nicovideo and Pixiv.
I think that it's useless, but I'll tell you just in case.No, I didn't really call for you.Suwako...MEMETAA?!Who is it that calls for me?HUAH!!Beware of what's coming from above.Your Shimenawa is a bit off, you know?(Monotone)Kanako...