Tennis Biathlon is the 109th episode of the original Prince of Tennis. It originally aired on the 19th November 2003.
A special training session awaits.
The team is still at the cottage and they are practicing against each other all with great movement and power. The camp is coming to an end but Coach Ryuzaki comes up with a "special menu". A biathlon. They will go through a series of check points and the first one to finish is obviously the winner.
They run along coming to the first clear point where Kachiro waits. The first checkpoint comes along where you have to reach a dropped ball 25 meters away. The second checkpoint is where Horio waits where he shall test the control you have while seriving.
While the Seigaku regulars are battling it out, Coach Ryuzaki and Shiba go ahead to Atobe's (Hyotei Acadmey) mansion and tennis club to ask them to come over and have practice matches with the Seigaku regulars. Again we go back to the biathlon and find out that the last test belongs to Katsuo and he tests the power of the players shot by using the resistance of a river.
Everyone continues running to the finish line and they find out that the whole purpose of the camp was to overcome everyone's weakness and that's just what they did especially with the biathlon.