Imouto wa Shitteiru - Vol. 1 Ch. 1 - The Man Named Kiichiro Miki

[Pen3]

This is not actually a problem. All of the characters are distinct. (Trust me I have issues when they're not.)

Not unfortunately. Their scanlation is very readable and got me to buy the series.

His sister and his coworker look alike, but the iris is very easy to differentiate for me.

 

[aa11bb]

Why do I feel like I've seen this art style somewhere before? Looks familiar.