A young man

[Gaya87]

A practical student is also called an industrial trainee I think. The term "intern" is relatively recent.

I decided to remove the word “who” because I felt that the sentence is hanging. To me the sentence is good without the word “who”. Any feedback on that?

Shika, an intern student in his company, joins him in the search.

 

[tedmc]

During the journey, they develop a relationship, but their romance meets with obstacles when Shika keeps a secret.

I find it hard to relate the keeping of the secret and the romance meeting with obstacles.

Perhaps, you can say:
During the journey, they develop a relationship, but their romance meets with obstacles arising from a secret that Shika keeps.

Shika, an intern student in his company, joins him in the search.

An "intern" will do. An intern is a student.