Yeah, that guy truly does look like a 28 y/o from the 2000s.

A couple things to note about Spirit Contracting as a Technique. Post-spirit-catastrophe, supernatural entities have mostly been beaten back into the shadows or culled entirely. Owing to that, as well as the whole 'the more versatile a technique is, the weaker its general potency' deal, Masashiro would probably mostly gain his contracts from nascent tsukumogami, rather than anything properly sentient. So maybe like, floating spectral teacups or stuff like that. For 'powerful' spirits, its less a matter of forming a contract with them and more of finding them to begin with.

Since he's a proper adult during the worst times, he probably has had at least distant friends and family killed/possessed/drained by spirits during the catastrophe, or subsequently killed/robbed/organ-trafficked/enslaved by Lineages afterwards. Just something to keep in mind, especially if his hometown is a larger city. Heck, maybe they'd target him personally specifically because he's a hackerman.

The Agency itself doesn't really need 'proof' to act on things, especially if he does have a pattern of prying where he shouldn't. You can consider him to be on probation during this RP, with his fellow team members advised to act as his supervisors in case he's a Lineage plant for whatever reason.