Ciel~the Last Autumn Story~ Manhwa
I recall blitzing my way through the first 60 chapters. Halfway through, however, I found my attention slowly slipping. By the end of it I wasn't as engrossed reading the series than when I first started. It could've been the pacing, I guess. About the ending (no spoilers): Lesser time skips might've served the manhwa better and made it a more comprehensive read. All in all, it's a grim story made even more tragic by the choices the characters made near the end...
Mikado no Shihou
I do understand that she's short for her age, but must she look like a 10-year-old?
Namaikizakari
Author's pen was doing just fine...but it must've started spitting out too much ink halfway through. It was plenty decent and their high school days weren't a drag to read...but now they're in uni, it feels like its gone on for too long you start wishing it was over with.
Magi
That cursed final arc... (;  ̄Д ̄) It seems that Ohtaka-sensei paved a road for the grand finale but somehow veered off the track, and it made the last arc a mixed bag of sorts... it simply wasn't up to par with everything else.
Kasane
An interestingly unique idea that took a life of its own. A bloody good read that had a mediocre second half, much to my dismay.
Wind Breaker
Note to self: Available on Webtoon.. The full-on adrenaline that got me into this series was all but gone by the 200th chapter. More races like those in the first 100 please.
Usotsuki Lily