This is your first fanfic? The writing skill and clarity is even more remarkable then. Well done.
I will admit to being curious as to why Kagome is wearing a yukata and as to the location of the rest of their corresponding parties, but the information truly isn't necessary to enjoy this short fic.
Writing-wise, my only thought would be to remove the word "passionately" from the following sentence: "In the space of a heartbeat, his warm mouth was pressed passionately against hers." The affection comes naturally in the description afterward, so it isn't necessary to add the adverb at the beginning. But this is a minor tweak and personal opinion. Ignore as you deem fit.
Content-wise, I've never found the ground on a meadow to be warm when laying upon it. Soil tends to be cool and wick away body heat. I live at the nothern end of the plains states, so I feel fairly confident in my observation. But just because the ground is cool doesn't mean a person won't cook in the sun.
All in all though, wonderful job.
