The romantic relationship between Shuyin and Lenne is quite unique. Their love for each other was so powerful that even the phrase "until death do us part" could not defeat it. Shuyin was madly in love with Lenne; he would do anything to protect her. Alas, they parted their world and each other with unanswered questions, and unspoken words.
Shuyin is the game's main antagonist, but he originally had good intentions. He was sick and tired of watching people close to him suffering because of the war. He only wanted to save his love, Lenne, which is also his greatest downfall. He is similar to what we call a tragic hero. He could have succeeded in destroying the world using the Vegnagun; however, it was Lenne, the same person whom he was trying to save, who stopped Shuyin for activating Vegnagun.
Lenne knew Shuyin loved her. However, it wasn't the same for Shuyin. He struggled to save Lenne, yet she couldn't tell him that she loved her from the depths of her heart. Because of this uncertainty, Shuyin remained an unsent. Over time, his feelings intertwined with the pyerflies, and became a ghost.