Su Zimo chose to follow the three Execution Guards not because he was afraid of them.
However, he was frustrated and could not let go of Ji Yaoxue's departure.
Even without the three Execution Guards, he was prepared to leave Astral Sect.
Since he was targeted by the Execution Guards once more, he would let nature take its course and board the immortal boat to leave Astral Sect with the three Execution Guards.
Initially, Su Zimo did not take the mission mentioned by Commander Liu seriously nor was he interested.
However, he vaguely heard the name Meng Yao and found it familiar, as though he had heard it somewhere before.
At that moment, Su Zimo's thoughts were in a mess.
The scenes of his interactions with Ji Yaoxue flashed through his mind from time to time. At times, he was puzzled as to why Ji Yaoxue's cultivation would stagnate. At times, he was thinking about his future plans.