hi anon!! first of all sorry this took long, i forgot to check this account 😭 but yes! i have a few Opinions and Thoughts about them..

i think they see in eachother traits they admire and both posses, such as being very disciplined and hardworking, and since they have a cordial and respectful relationship, i can see them enjoying each other's presence especially during work.

however... if i'm not wrong it's said in canon that ludwig has a hard time understanding kiku, and i really get why: lud is very straightforward, direct, and understands things quite literally, while kiku is the opposite - he rarely expresses his opinions, tends to sugarcoat things, has difficulty saying "no", and in general is very prone to express himself in vague ways. (except for the times his repressed feelings win and he ends up having very dramatic outbursts, which is something that happened to him in canon while having a disagreement with ludwig kgjfjg)

in my interpretation this might be an obstacle for them to develop a deeper bond and might cause misunderstandings between them. in any case, i like to think that kiku has a genuine fondness for ludwig (and might even feel sorry for him at times for considering that his work as a nation and the role he plays inside the european union forces him to carry a burden way to heavy at his young age), while ludwig admires him and is always eager to learn from him.

on a more shallow note, i like how they look next to eachother and their height difference, i also like to think that kiku has a soft spot for big men who seem intimidating but are softer than they look (?)

lastly, i have to mention that i love their roles in the cardverse,, king of hearts ludwig married to queen of hearts kiku is such a great concept omg it has sooo much potential, i can see ludwig developing a crush on kiku, or maybe getting nervous when they first met - their first encounters might be a bit awkward, but little by little they end up developing a strong relationship and bring their kingdom to prosperity...

so in conclusion while i find it a bit difficult to see them as close friends i do think their relationship can be very interesting once it's explored, but like i said this is my interpretation so anyone is free to disagree! and thank you for the question anon ! ♡