Listening some radio interview at NicoNicoDouga, they explain that shi reference to ´death´. No the end of the band, more like an end of a musical cycle.
The radio interview is itself very interesting. They talk about Ringo in a very reverencial way. They give a shot and invited her about a collaboration, but with little hope (one of them has worked with Shiina Junpei, which probably helped to smooth things). When Ringo agreed, they actually felt cornered
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Shiina Ringo seems to give this vibe of commanding, I don´t know how to word it. When the boyband Tokio went to Music Station, their vocalist, Nagase, talked about how he would act totally like a junior around her (when he recorded her music) and would found out later that they are the same age. "I was tricked by her aura".