No titles and no hierarchy! That's what startup founders say, isn't it? But when the company grows, or when outside stakeholders put pressure on the startup to conform to established notions of leadership, it is good to know what to say and why you've made the choices you've made.
There comes a point when the founders can't answer every question and have an opinion about everything - there's simply not enough time. Nobody wants a micromanaging boss over their shoulder, but people do need guidance, coaching, someone who gives them feedback and challenges them further. How will you arrange that?
Figure out who has those leadership functions in your company, and if they are serving your vision. Leadership is always somewhere. Make sure you're in charge of where it is and how it is used.