チリヌルヲワカ / Chirinuruwowaka: 陰日向 / Double-Faced
Check out KOH3956's awesome cover of this song!_____
Title: 陰日向 / Kagehinata / Double-Faced
Band: チリヌルヲワカ / Chirinuruwowaka
Album: アヲアヲ / Awoawo
Lyrics: ユウ / yuu
Composition: ユウ / yuu
Japanese lyrics: http://petitlyrics.com/lyrics/2409582
This song has some really interesting writing. There's a clever use of synonyms that sound similar, but have slightly different meanings all over this song. (隙間/狭間, 衝動/行動/鼓動)
The song also uses the expressions 雲行き (Movement of the clouds) and 風向き (Direction of the wind) at different points in the song. Again, these are similar and theme, and are actually both metaphors for "the situation" or "the outlook of things".
Finally, there's the part about becoming a shellfish. I couldn't find this as a common expression, but I did find one interpretation of the expression in an unrelated context. It can mean to not talk to anyone, not be affected by anyone, and simply live in your own shell. So the singer says: "When you feel like pulling away, come see me and I'll make you feel better".
Image is from Chirinuruwowaka's website