In case the official site ever goes down, I screencapped an important piece of information. >
link
Toei revealed the real title with setting up their Aishite Knight dedication site. Since the katakana writing for "night" and "knight" are identical, there were always both versions floating around on the internet. Eventually, "Aishite Night" prevailed. I'm really glad to know that the real name is supposed to be "Aishite Knight".
I'm surprised that main sources (like wikipedia, ann, anidb, et al.) didn't adapt this, yet.