The setting of this story is also the same as the anime, "Shin Tennis no Ouji-sama": The Japanese U-17 (under 17) High School Representatives Selection Camp.
The protagonist is a certain publisher's rookie female reporter. Not having a clue as to what's what, she gets selected to become an interviewer for a project.
As for this "project"... The project, "New-Generation Players Grand Prix", will involve 30 of the U-17 Japanese Representative Player Candidates fighting for the #1 spot in both name and substance. Within a limited time frame of 7 days, the reporter is to completely cover and collect information of the players and publish it as an online article. The #1 player will then be selected by the readers' votes.
After a series of various events and interacting with the players' "true selves", the protagonist grows closer to the players. Depending on the level of completeness of your everyday reports you upload, the level of attention the players receive fluctuates and changes on a daily basis, as does their ranking. Towards the conclusion of the reporting period, on the final day, who will be recognized as the #1 player?
And what will their relationship with you be?
...Your 7 days with the representative cadets will now begin!
[Translation of the official website plot summary.]