Mr. Viet will meet with you instead of Mr. Koichi because Mr. Koichi really hates you.
Remember how 嫌い is to dislike? When that dislike is big, you really dislike it. That means you hate (or really hate) it.
The reading is the reading for 大, and the reading for 嫌い is like the one you learned with 嫌い in level 20.