13y old me would be ecstatic to be gifted a GShock. If he’s deserving I might even upgrade this to an Apple Watch SE if you have the budget.

Just note that mechanical watches might not yet be appreciated by this age group. Likely they will not perceive the value. If you insist on mechanical go safe with a Seiko 5 to test the waters.

I would also recommend the Tissot Gentleman (automatic) if it is within your budget.

https://www.tissotwatches.com/en-en/t1274071605100.html

I presume this will be your partner’s first “serious” watch, so something he can dress up or down definitely is desired (something that the Tissot Gentleman can do esp. on a black leather strap).

If you want to stick to Seikoland the Presage series is also worth checking, albeit more expensive than the Seiko 5 sports.

https://www.seikowatches.com/sg-en/products/presage/srp837j1