the first person to say he loved kagome - kouga, the wolf demon
Kagome never had any romantic feelings for Kouga. It has always been Kouga loving Kagome. Kagome first met Kouga when he kidnapped her thinking that she would be useful in finding the Shikon no Tama shards. Upon that first meeting, Kagome was at first angry and hated Kouga. However, after learning why he needed her, Kagome started to showecompassion and concern for him especially during his his battle with his enemies such as the Birds of Paradise and of course Naraku. She would always treat him as a friend and ally.
However, that is where the issue was and what confused InuYasha the most. He wasn't sure if Kagome was trying to flirt with Kouga to just make InuYasha mad. Kagome was always polite to Kouga, almost to the point of leading him on, and protected him usually from a jealous, overly-confrontational Inuyasha especially whenever he is hurt. Kagome doesn't love him, though. She admires him as a close friend. However, his declarations of love and mating have left her feeling distressed about how to let him down easy. Because of Kagome's hesitation to turn Kouga down and possibly hurt him, she is often the cause of trouble and fights between Kouga and Inuyasha, and their mutual jealousy of each other's interactions with Kagome prevent InuYasha and Kouga from ever being close friends just comrads when needed, if ever needed.
In relation to Kagome, Kouga seems to be the "Houjou" character of the past, constantly pining after Kagome, showering her with praise and adoration, and seemingly unaware that his feelings are not returned.