Shrine: Couple: Reasons

Ken & Hikari - Dark & Light. You can't have one without the other.
Hikari, for me, has helped Ken ot overcome his darkness, and Ken helped her overcome darkness too.
When Hikari first heard about Ken as the Kaizer, she instantly hated him. Whilst Ken showed no signs of liking any of them, he -did- have all his TVs tuned in to see Hikari in different poses. He never does this for the others, only for Hikari. He also seems to like answering her back politely (He does for me, anyway). Some can say he's being sarcastic, but he still does it....
When Ken became kind, her Digimon, Tailmon, was the first to rush over next to Wormmon to check if he's okay. Hikari was very concerned at Wormmon.
The Dark Ocean was the one of the biggest reasons. Hikari begins to see the Dark Ocean, and appears in pain slightly. Later, she rushes to Ken's aid, along with Miyako. Hikari, however, was the only one to see the Dark Ocean with him and comfort him. She even puts her arm around him at one stage, something no one else in the show ever does, with the exception of Daisuke.
Later, when Ken is finally about to seal the Dark Ocean off, he's put in a lot of pain in doing so. Hikari was the first and, at one stage only person to rush to his side to help fight. She places her hand on his for support, and only after this do the others follow them.