A hot-blooded cavalry battle with 血の気が多い

Idiom Explanation: Being hot-blooded with 血の気が多い

During sports day, the events break for lunch. Lulu joins her friends, and they discuss the upcoming afternoon activities.

響子(きょうこ):: 「騎馬戦(きばせん)は特(とく)に血(ち)の気(き)が多(おお)いけど」; “The cavalry battles are especially full of hot-blooded guys, though.”
清美(きよみ):: 「うちは番長(ばんちょう)がいるから安泰(あんたい)だよね～」; “As long as the big boss is here, we're safe and sound, right~”

Key Points

1血(ち)の気(き)が多(おお)い = hot-blooded and quick to fight

Kyoko uses it for the cavalry-battle crowd: aggressive, excitable, and ready to clash.

2騎馬戦(きばせん)は特(とく)に sets up the comparison

騎馬戦(きばせん)は makes the cavalry battle the topic, and 特(とく)に adds “especially”.
The implied comparison is with the other sports-day events coming after lunch.

3Final けど softens the warning

Kyoko leaves the thought open with けど, giving the line a trailing “though…” feeling instead of a hard warning.

4うちは = “our side”

In うちは番長(ばんちょう)がいるから, うち means the speaker’s own group, not her house.
番長(ばんちょう)がいるから gives the reason: their big boss is there, so the group feels 安泰(あんたい), safe and secure.

騎馬戦 (Mock cavalry battle): 騎馬戦(きばせん) means a school sports-day contest in which groups form human mounts and their riders try to take opponents’ caps or headbands.
うち (I): うち can mean “I” or “me”, especially in Kansai speech and in casual speech among women. It also has other meanings, including “home” and “inside”.
番長 (Gang leader): 番長(ばんちょう) means the leader of a group of juvenile delinquents, especially in school settings. It can also be used playfully for the dominant or toughest member of a group.
安泰 (Peace): 安泰(あんたい) means safe, secure, and free from worry.