Tohru is shown to be rather well-balanced, using logic and sensibility to overcome things unlike the rest of the cast. He's described as a tsukkomi by Toki, otherwise known as someone who's much more reasonable and especially smarter than his following peers. It's been made clear that Tohru is rather sadistic and twisted, even outside of it being directly stated (for example, his endings and routes in the games). While he comes off as rather timid and nervous, it's more so his cravings for companionship and love that results in him behaving this way. Things don't unsettle him much, but Tohru Kunikuda still gets frightened easily and is actually prone to getting hurt in simple ways. He has rather bad trust issues, which is mostly understandable after his ties with Koshi Tanaka and his many negative past issues with both his parents and peers. Although he comes off as obsessive, or "yandereish" in nature, he's actually much more dominant and dependent than anything else. Possessive in nature, he's very needy and gets stuck with people easily, and because of this, he has a hard time making friends and being around other people. This may have been why he opened up to Yukari Minamida so fast. Oddly enough, he prefers being alone despite his yearning for friends and company. Obviously shown throughout the games and within his backstory, it's clear that Tohru isn't the happiest kid in the school. Whether it be because of pressure and force from his parents, Koshi Tanaka, loneliness, or overall mental issues is unknown. It's clear he also has a caring and sensitive side deep down, or else he wouldn't of worried so much for Minami Minamida's safety (although this was mostly because of care for Yukari). He's very determined to build up the Occult group into a proper club, stating he believed he could do it if he really tried in Liar Liar: Pants on Fire

I imagine he would be very timid, I can see him with a more feminine voice or a normal male voice.