1For one substance to dissolve into another so completely that they become one; used for physical or chemical mixing.
インクが水にすぐに溶け込んだ。
The ink dissolved into the water right away.
バターがフライパンの中で溶け込んでいった。
The butter melted into the pan.
出汁の旨味がスープ全体に溶け込んでいる。
The umami of the dashi has permeated the entire soup.
2To naturally adapt to a new environment or group so as to blend in with those around you; commonly used when talking about transferring schools, moving, or starting a new job.
転校生はすぐにクラスに溶け込んだ。
The transfer student quickly blended into the class.
新入社員が職場の雰囲気に溶け込めるよう、先輩がサポートした。
A senior colleague helped support the new employee so they could fit into the workplace atmosphere.
彼女は留学先の文化にすっかり溶け込んでいた。
She had completely blended into the culture where she was studying abroad.