Should I tell a girl I’ve been one one date with that I’m seeing someone else casually

So I’ve been seeing a girl casually for about 2 months now. Let’s call her Emma. We are chill have fun, it’s my first “casual relationship” if u call it that. We have communicated that we are good to see other people just to make sure to tell the other if we sleep with another for health reasons obvs.

I’ve been talking to a girl let’s call her Kim. We’ve been talking for a little under a month, we had our first date this past week it went good, I’m not sure if I want to date her yet I would like to get to know her more.

I know Kim intends to date to find something long term, I am open to something long term and want to continue to see if I could have that with Kim but I am still currently seeing Emma. I know it’s only been one date and I don’t know if I even like Kim like that but I feel soo guilty still seeing Emma. But I also like things with Emma as shitty as it sounds.

So my question is should I tell Kim that I’m seeing someone casually? If so should I message her it before we go on a second date, should I do it on the date or later. Idk I just feel shitty to Kim about it. I’d be down to end things with Emma if I truly felt like I could have a good relationship with Kim but personally it’s too early for me to know now so idk what to do. I want to tell Kim but maybe it’s not needed yet become it’s so early?

I swear I’m not a fuck boy lol it’s all so new to me I don’t want to hurt anyone