I just wanna say, I love how you've kept Tei a yandere without being outright evil like she is in a lot of fanfics/songs. A lot of portrayals of her make her unsympathetic or just outright hard to sympathize with, but you've kept her a likable character who just makes questionable choices.
Ah, I missed the last few updates! Having read them -
D'aaaaaaw! I like the departure from Tei's usual portrayal; she'll go to great lengths to get Len's attention, but realizes when she's gone too far and takes a step back until Len's ready to initiate. That ending was perfect and so, so sweet. We all need us a Len-kun.
(I also liked the reference to girls only wanting to date him for his fame, sad though it was - I've also got this headcanon that Len's an intense romantic that nevertheless had trouble finding love for years for that very reason.)