Japanese for “can’t”, usually used in the Japanese learning community to refer to those who aren’t able to learn the language or reach a decent level of fluency.
Kimi Wa Dekinai Ko (Japanese, 君はできない子, translation, You Are a Useless Child) is a song made by Kikuo featuring the beloved Hatsune Miku using singing voice synthesizer Vocaloid.
The song is about a mother constantly insulting her child by calling them a "useless child". At the end of the song, the child either disappears, dies, or (TW) commits suicide depending on how you interpret it, causing the mother to blame herself in the end and calls herself a "useless child".
Fun fact: Kimi Wa Dekinai Ko is Kikuo's 14th vocaloid song.
Romaji: Kimi wa dekinai, dekinai, dekinai ko, kono yo de ichiban dekinai ko.