YOU SAID:

Sonic looked into my eyes tentatively.

INTO JAPANESE

ソニックは暫く私の目を覗き込んだ。

BACK INTO ENGLISH

Sonic looked into my eyes for a while.

INTO JAPANESE

ソニックはしばらく私の目を見ていた。

BACK INTO ENGLISH

Sonic was watching my eyes for a while.

INTO JAPANESE

ソニックはしばらく私の目を見ていました。

BACK INTO ENGLISH

Sonic was watching my eyes for a while.