Intelligent Weapon
You are an intelligent weapon, and you have a companion that equips you.
Combat is mostly your ability, and you can strengthen your companion. You may also provide some magical abilities.
Your companion does social activities (conversation, etc.), but you can give telepathic advice. Your companion and you have separate knowledge skills.
It is assumed that not just anyone can become your companion. In this case, if your companion dies and is not revived, you will "die" just like a normal class character. Whether a new companion will find you and equip you will depend on the story.
In this case, it may not be much different from creating a "fighter who owns an intelligent weapon at level 1" and doing a special roleplay.
It would be more noticeable if you could easily change companions. In this case, you may need to set up some kind of "death of intelligent weapons".