エイは育ち、僕はプロポーズに鉄を曲げる (Ei wa Sodachi, Boku wa Propose ni Tetsu wo Mageru)

Background
His endurance. A song by Takahashi You about losing a ring before a proposal and fishing madly to retrieve it from the river it fell into.

This song has entered the Hall of Fame.

Trivia

 * Humorously, Sekihan can be seen alongside Roro in scenes of both PVs, suggesting that the events of both are happening at the same time.
 * Unagi Pie (うなぎパイ) is a type of confection made partly from eel.