Mafuyu was adopted by Tomo's father and decided to protect Tomo to repay her father for adopting her. Mafuyu and Tomo have been friends since childhood ever since. Because of this, Mafuyu is very protective of Tomo and won't let anyone harm her, verbally or physically. Tomo loves Mafuyu dearly, and wishes for her to be happy, not wanting to be a burden to her. Despite their smaller size, Tomo has a habit of playing with Mafuyu's breasts.
Unlike with Mafuyu initially, Sasha takes to Tomo immediately, due to her resemblance to his sister figure Olga. Tomo likes him just fine, and believes him to be a kind boy, despite his cold attitude.
Despite Jita attempting to kill her (in the manga), Tomo forgives her immediately and they become friends. Tomo isn't aware of Jita growing a crush on her. This crush is expanded upon, but exaggerated to comedic levels in Seikon no Qwaser II.
Tomo loved her father dearly, but as a child, she noticed the darker side of his personality. While he was outwardly kind and strong like any parent, he seemed only cared about things that were beautiful to him, and therefore, didn't love her the same way he would a greenhouse he once built. Tomo cared about the area the greenhouse was built in, but he without hesitation or the slightest bit of care, had of many forest creatures driven from their homes or killed, and tore down many trees to have that greenhouse built, showing some level of emotional abuse to Tomo.