How I feel mentally when Niki is called Nikki for some reason:
What I do about it:
Btw, just since it hasn't seemed to come up, on top of having Sensei recall his name, she also has him recall the place the accident happened, and it was Niki's letters delivered by Noriko that actually brought back Sensei's first confirmed memory of the past, which happened to be the night he first kissed Niki:
Niki definitely seems to fit the
one true love cliché better than anyone. It's probably why Maya Prime and New Maya both feel threatened by her:
She's his childhood best friend, first real girlfriend (kind of hard to count Sekai), and is seemingly only rivaled by Chika (Miss Maximum) in sexual compatibility with Sensei. Currently she's taking care of Sensei's niece and might even move in.
New Maya is in for a brutal awakening once she realizes what Sensei's been up to. Chika and Maya (in particular) are kind of Niki blind at the moment, but we'll see for how long.