Going from fighter to Magus Kensai, it says:
A kensai is not proficient with armor or shields and suffers normal
arcane spell failure chance when casting magus spells while armored.
But as a fighter, I'm proficient with armor. Will I still suffer from spell failure?
A magus is also proficient with light armor. He can cast magus spells
while wearing light armor without incurring the normal arcane spell