成人 and 未成年: adult audiences and guardian consent
Read a course for adults, growth into adulthood, a protagonist still underage, and participants who needed guardian consent. Keep the audience and status separate from whether consent was obtained.
成人 identifies an audience and growth into adulthood
成人 (せいじん) means adult. In “この講座は成人を対象に開かれている。” (“This course is offered to adults.”), the course is offered to adults. 成人を対象に identifies the intended audience, rather than reporting attendance by every adult.
In “物語は主人公が成人するまでの成長を描く。” (“The story portrays the protagonist's growth into adulthood.”), the story portrays the protagonist's growth into adulthood. 成人するまで gives the scope of that growth; it does not place every event after the protagonist is already an adult.
未成年 describes being underage
未成年 (みせいねん) means minor or underage. In “物語の主人公はまだ未成年である。” (“The story's protagonist is still a minor.”), the story's protagonist is still a minor. まだ keeps the description with the person's continuing underage status.
The adults addressed by the course and the minor in the story belong to separate examples. The words alone do not identify the same people across the scenes or supply an exact legal age threshold.
A consent requirement is not consent obtained
In “未成年の参加者には保護者の同意を求めた。” (“Underage participants needed a guardian's consent.”), underage participants needed a guardian's consent. The English wording states a need for consent, while the Japanese 同意を求めた reports requesting it.
Both a request and a requirement are distinct from obtaining consent. The sentence does not establish that a guardian agreed or that every participant had already supplied consent.
Does 未成年の参加者には保護者の同意を求めた establish that guardian consent was obtained?
Show the answer and why
No. The Japanese wording reports requesting consent, and the English sentence describes consent as needed. Neither establishes a guardian's agreement or completed consent.