A successful parade with 成功
Kanji Explanation: Becoming and accomplishing with 成

Yui’s class is participating in a parade at a festival. Yui wonders if Sacchan and Kotoha will come to watch.
- 結衣:
- 「リーダーとしてパレードを成功
( させないとっ」- “As the leader, I have to make sure the parade is a success.”
Key Points
成功
( is success as an achieved outcomeBy itself, 成功
( means success or a successful result.In this scene, Yui is focused on the parade turning out well.
成功
( させる means to make something succeedThe causative 〜させる turns success into something the speaker must bring about.
パレードを成功
( させる means make the parade a success.
ないと and とっ convey pressure and determination
〜ないと is a casual way to say have to or need to.
リーダーとして frames this as a role-based responsibility, and the clipped とっ gives the line urgency.