Moteki (2010)

we all like a nerd underdog love story. but this one doesn't have the internet.

Both have male-centric erotic comedy/hentai elements with a first-person voiceover of the protagonist's inner thoughts.

I recommend this drama just because both use iconic japanese music as part of their narrative, the difference though moteki used music from all era not just 90's.

Both follow the perspective of a nerdy male lead who has issues with dating.

Both contain a dorky loser of a male lead trying to navigate life and dating. Both contain a movie about the show as well!