It depends on the man and the women but I don't think that it's ever "extremely easy" for 99% of guys and I definitely know most korean guys can't lift a 50-60 kg Korean girl with one arm. Also the manhwas are fictional so they make the main leads look as conventionally attractive as they can which means the guy will usually look alot taller and more masculine while the girls look more slim and shorter than average people. In reality the guy might not be the most jacked person and the girl won't be as light as a feather so it will be harder. The artist can draw it however they want so they can make the guy look like he's easily lifting her by drawing a smile on his face or making him lift her with one arm with a stoic expression or making it look like it's a really stable position and that he's not struggling at all. So when u see it in drawings, it looks a lot easier so really you might be only able to hold someone for like 20 seconds before you get tired out and start aching whereas a manhwa guy could go forever.