One Sided Love?

My Neighbour Can't Sleep 

Go Go Squid! 

Doctor John 

Touch Your Heart 

You Who Came from the Stars 

Perfume 

Love in Sadness 

 The Beauty Inside 

Goblin 

Because This is My First Life 

IN NO PARTICULAR ORDER

|Long Daily/Family KDramas|

Ugly Alert (Second couple) (Don't know you watch daily dramas or not but this one has the most longest one sided love troupe ever, literally I'm the fan of same troupe as you so I think I know what you're looking for! So, this one literally made me watch those huge number of episodes!)

My Golden Life (Second Couple) (He's love with her sister first for a long long time. Later, he falls for her.)

My Daughter Su Yeong (Second Couple) (She's been in love with him forever but he's stuck on his first love and they almost get married too. But later he marries her and falls slowly for her too.) 

Smile you (Family Drama, he loves her sister, woos her for long time before he falls in love with her too)

|Normal Short Weekly Kdramas|

Wedding (2005) (He's in love with his childhood friend even after he gets married, and even says he won't love anyone else if not her in front of his wife)

My lovely Kim Sam Soon (He's in love with his ex gf for a long time, even gets together with her when she returns while female lead keeps loving him.)

Prime Minister and I (He's still stuck in love with his dead wife while he gets fake married with the female lead.)

Warm and Cozy (He's in love with his college friend while breaks female lead's heart most of the time)

Which star are you from? (He remains in love with her sister for a long time while he treats her as a kid)

Secret Life of my Secretary (He's in love with some other woman who happens to be the other identity of his secretary)

Attic Cat (He's in love with someone else and yet uses female lead when he needs)

Rich man, poor woman (He's still stuck on his first love while female lead works as his secretary)

Another Miss Oh (He's stuck on love with his fiancee who left him on the day of his wedding and so doesn't accept female lead's feelings for him)

Full House Thai ( Thai drama, He uses female lead to make his gf jealous, remains in love with her for a long time and so breaks her heart so much)

Buzzer Beat (Japanese drama, same troupe that you want)

Love so beautiful (Chinese Drama, similar as Itazura no kiss)

My Neighbor can't sleep (Chinese Drama, cold male lead so doesn't accept her feelings.)

|Special Mention|

Our times  (Taiwanese movie) (they both like somebody else first, but female lead falls for him while helping him woo his crush. Its one of my favorite movies so far, you'll see why once you see it yourself.)

I'll recommend more if I remember something else!

I will sort these by how well they fit with your request/ the other ones you liked: 

Unrequited Love  (C; you can guess from the title) 

A Love so Beautiful (C; someone mentioned above, similar to Playful kiss, really cute though) 

Attention, Love! (TW; also extremely similar to Playful kiss, not in a boring repeating kind of way though)

Good Morning Call (J; since we‘re still on the theme of school and living (close) together, this one fits well, the female lead is really refreshing since she‘s not as overbearing as the one in Playful kiss) 

Gogo Squid! (C; not school/university at least not entirely, still really really cute though, and probably exactly what you‘re looking for) 

Sweet Dreams (C; this one is more like fangirl meets idol, but still same kind of feel) 

Alright so these three I wouldn’t necessarily count as one sided, since that not really the main element at least but there’s still parts of it, and their pretty good. 

The Masters Sun (K; even if she‘s not inlove with him at first she is kind of obsessed with him) 

The Liar and his Lover (K; for this one it definitely is one sided love, mainly based on music, however I think the dude realises his feelings quite fast) 

Because this is my first life (K; also a living together kind of Szenario, coincidentally with the main actress from Playful kiss (Korean version)) 

Itazura na kiss