A Small Leak Will Sink A Great Ship. I (TBA TBA): is the 66th chapter of the manga written by Kore Yamazaki.
Marielle discovers Lucy is suffering from the same drain magic effect that Simeon is. Chise wants to help discover who is behind the attacks but Elias has something to say about that. Chise and Philomela have a small bonding moment over refilling her potpourri bag. The students take a supplementary class on Runes. Zoe visits Lucy in the infirmary. Chise visits Silky back home in preparation to meet with someone.
Marielle visits Lucy in the infirmary and uses witchcraft to discover that she is also suffering from the same draining effects that Simeon is. Chise learns about the Testament of Carnamagos for the first time. Elias has attempted to trace it since it absorbs magic, but it appears to be using a concealment method, making it difficult. Alexandra, Elias and Marielle discuss how Chise is able to keep Lucy alive just by being in proximity to her, since Chise's magical production as a Sleigh Beggy is greater than the rate of magic that is being drained. Chise feels compelled to be involved with finding out who is behind these attacks. However, Elias tells her this is a case that does not involve her and both he, Marielle and Alexandra tell Chise this is not a situation that children should be a part of.
Philomela is nearby and informs Chise that her potpourri bag's scent is weakening. Chise offers to refresh it, noticing that the bag is worn, indicating that Philomela carries it around with her. They agree that next time they will make bags using different scents together.
The students take a supplementary rune class, discussing the relevance of ancient languages and how understanding them is important to mastering the rune's full potential. Chise picks out a rune that looks like a thorn. In old Norse language, it means "thuriaz" and is said to be derived from either a giant, a fairy or the Thor's hammer. The modern way of saying the word is "thorn". Zoe inquires about a rune that looks like the letter "M". It is called "ehwaz" and is known as the horse rune. Since it carries a rider, it implies movement and represents making progress. The students are instructed to choose a rune that is comparable with their intention.
That evening, Zoe visits Lucy in the infirmary after Chise notifies him that she collapsed shortly after waking up. Lucy becomes intrigued about Zoe's snakes and asks to stroke them. A shocked and embarrassed Zoe complies, removing his head phones and allowing his hair to transform into snakes. Lucy pets them while reminiscing about having spiders as she falls asleep.
Chise goes back home to the Ainsworth cottage and visits Silky to explain what is happening at the College. Chise is happy that Elias has someone he considers a friend, seemingly proud of his progress. Chise heads outside the cottage to search for branches of haze.