S'yne's Sister/Relationships

Naofumi Iwatani
While Naofumi and S'yne's Sister have opposite goals, S'yne's sister has actually been quite helpful to Naofumi. She often goes out of her way to explain her organization's technology and its weaknesses for Naofumi to take advantage of. However, to Naofumi, she is still a highly dangerous, unpredictable enemy. She was surprised when seen S'yne and Naofumi together. Before Naofumi time travel she say him to run, but only Naofumi hear it (from his own words).
 * Always calling Naofumi as "Iwatani".
 * She told Naofumi that he need to know reason when S'yne follow him, but only S'yne must explain it.

S'yne Lokk
S'yne absolutely despises her sister for her betrayal to the leader behind the waves. It is due to her sister that their world has been destroyed and S'yne has been reduced to a nomad across the worlds. When in comes the S'yne, her sister's masochist side come out as she been seen beating her S'yne for her own entertainment. When she catch S'yne sleep in L'Arc castle, she was gentle to her and mentioned, that she know many S'yne secrets, but if she expose them - S'yne became more reckless in her revenge.

Malty S Melromarc, Mald, and Lesty
S'yne's sister wouldn't care less if this group died, however they earned favor with S'yne's sister's leader and thus has been put under her leadership.

Hidemasa Miyaji
S'yne's sister couldn't care less about Miyaji as he is only a low-level thug in her organization which she could easily manipulate. She intentionally told Naofumi Miyaji's weaknesses and had no reaction to Miyaji's death.