I saw in a manga **ミIナト** meaning *minato* a name but I don't know what the character between **ミ** and **ナ** means and the usage of it

and theres another one too **おまさてI** and theres like 3 lines below it's written downwards

I'm not sure if its a mi katakana or what[![enter image description here](https://i.stack.imgur.com/vW5NU.jpg)](https://i.stack.imgur.com/vW5NU.jpg)

and what does that **S** like symbol mean?
[![enter image description here](https://i.stack.imgur.com/5ZHKe.jpg)](https://i.stack.imgur.com/5ZHKe.jpg)