Uwa-chan (im calling her "uwa") has a big similarity with Ura-chan in the appearance [lol their hairs are almost the same but one of them has a darker hair and a cat ears] this makes me to think that two characters are connected to each other i cant properly figure out in how theyre connected but one of the scenarios could be like uwa-chan is from the past of the situations happened in the song of the chikyuu no ura and shes basically ura-chan but in the past maybe she have been caught by some alien (isei chan) while have been waiting in the bus stop then she put her in the cage ?? we can look up to these songs lyrics and the song itself and we can find some similarities in these too like uwagaki got the lyrics like "The ending song, just kept repeating itself." and chikyuu no ura got "I spat all over and turned it, the pattern of the card remains the same" these two songs got deep meanings and these two songs has a similar melodic ending two of them is speeding up in the end