Ise Natsuki (伊勢夏樹) is a second-year center in the Kanagawa High School Rugby Club, though he plans to one day switch to a forward position. He began rugby in high school after being invited to join the team by Hachiouji.
Despite being a former delinquent, he is rather shy and extremely ashamed of his brother's rudeness and downright disrespect for rugby players. He works hard in practices because rugby is an escape for him, away from worries and from his brother. But he doesn't actually blame him because his brother has been his legal guardian for 6 years already, as he decided not to let Natsuki live with their uncle in Kyushu.
In episode 15, Ise becomes extremely frustrated with his brother for being against him going to training camp again because, unlike Ebumi, Natsuki is from a poor family, and thinks that at 16, Ise should quit school and get a job instead. Ise later got so incensed, he threw a glass near his brother. Knowing a fight would break out, he told Hachiouji to leave and said that he was quitting the team. He then later changed his mind, when Ebumi gave him cash, so that he could carry on playing rugby.
Before they joined the rugby club, Ebumi and Ise were often seen hanging around each other. They are considered the delinquent duo of the team.
Ebumi encouraged Ise to stay in the rugby club and lends him a considerable amount of money to allow him to do so. It got to the point where he actually lends him weekly 'wages' (allowances) to shut his brother up.
Hachiouji is the one who invited Ise on to the team which is why he thinks it is his duty to help out Ise get permission from his brother to go to the Summer Training Camp (chapter 37).
Since Hachiouji goes out of his way to help Ise it can be seen that he holds great respect for Hachiouji. In chapter 38 when they go eat lunch at the coach's house, Ise makes a plate of meat and offers it to Hachiouji, stating that it was cooked perfectly.
- Natsuki is popular with the Hachioji family
- His older brother is 10 years older than him, and in episode 15, it was revealed that Ise's parents died six years ago, the reason he is completely against Ise playing rugby is that it is a full-contact sport with risk of injuries, plus the mere fact that training camp is expensive.
- When Ise was a first year, he actually wanted to play as a flanker, but because the team was saturated with forwards last year, and many first years already has a forward position assigned this year (due to lack of actual players with experience as any position in the front 5 (props, hooker and locks)), Ise was stuck being a centre.