Explanation
Emphasizes the importance or uniqueness of something or someone; 'precisely', 'exactly', 'it is...', 'of all...'.
Formation
Noun + こそ, (Verb-て + こそ)
Detailed explanation
The ～こそ grammar point is used to emphasize the importance, uniqueness, or the most suitable thing or person in a specific situation. It can be translated as 'precisely', 'exactly', or 'it is...' in English. In practice, it most often appears after a noun (e.g. 今日こそ), or with verbs in the て-form (e.g. 頑張ってこそ).
Examples
Kyou koso benkyou shinakereba narimasen.
Today, of all days, I must study.
Anata koso watashi no ichiban no tomodachi desu.
You are precisely my best friend.
O-kane ga nai koto koso shiawase no hiketsu de wa nai ka.
Isn't not having money exactly the key to happiness?
Kare koso masani puro no kashu no you ni utaeru.
He can sing precisely like a professional singer.
Practice
Grammar content sourced from hanabira.org.