Nasu Veronica is an A-rank support built around Swarm stacking, attrition damage, and ghoul-based team utility. He is not a standard competitive PvP pick in the current environment, but he can still be a useful budget option for newer accounts that want sustained pressure, passive chip damage, and some support for longer fights, and can work really nice with Thanatos SS.
As a niche sustain-oriented debuff support who can perform well in beginner or off-meta teams that appreciate gradual battlefield control and passive value, his main issue is that he is slower and less explosive than stronger modern supports, so while he can be effective in progression and themed compositions, he usually falls short in optimized PvP where faster and more reliable utility units dominate.
But the main problem is that we can’t get copies of Nasu, yes, we can’t, there are no events. And the worse part, is that the unit is bugged, there are a lot if freezes when Veronica is in the field. So, just skip this unit.