"Lion Heart" was described as a soul pop-inspired bubblegum pop song by Billboard.
[1] It embraces a 1960s American retro sound and has a jazzy melody as well as "an ear-grabbing bass line".
[5] The music video narrates a story where the members of Girls' Generation each fall in love with a male protagonist, who turns out to be the same man (with his head being that of a lion, representing the song's conceptual "lion heart/lyin' heart" pun).
It's a decision that further shows how Girls' Generation is embracing change in their eighth year..."[8] The song was deemed the 7th best K-pop single of 2015 by PopMatters.
It was nominated for Song of the Month (September) at the 5th Gaon Chart Music Awards, but lost to iKon's "My Type".